Midlife

The higher candlepower lamp may be hotter in actual temperature than the 194 bulb, and may cause your blue diffuser to melt...just a thought.
You might want to consider LED bulbs as a replacement for anything but the alternator indicator lamp, which requires an incandescent bulb to work the voltage regulator.

Get the body in shape, including everything that is structural.  Without that foundation, everything else will be harder to do.  Once done, concentrate on getting it to be a roller (brakes, steering, suspension)  so you can trailer it to a paint shop in the future.  Before paint, make sure the doors, fenders, windows, etc. all fit correctly.  Then after paint, consider installing the wiring next, then the engine and interior.  It will be a long process...so be patient.

OMG!  With all that's missing, methinks you've been out in the sun waaaay too long!
Just remember, when you come back pissing and moaning about something, we'll remind you about how much you love this stuff!

Get the body in shape, including everything that is structural.  Without that foundation, everything else will be harder to do.  Once done, concentrate on getting it to be a roller (brakes, steering, suspension)  so you can trailer it to a paint shop in the future.  Before paint, make sure the doors, fenders, windows, etc. all fit correctly.  Then after paint, consider installing the wiring next, then the engine and interior.  It will be a long process...so be patient.

Get the body in shape, including everything that is structural.  Without that foundation, everything else will be harder to do.  Once done, concentrate on getting it to be a roller (brakes, steering, suspension)  so you can trailer it to a paint shop in the future.  Before paint, make sure the doors, fenders, windows, etc. all fit correctly.  Then after paint, consider installing the wiring next, then the engine and interior.  It will be a long process...so be patient.

867-5309

Awww shucks.  Thank you!

A common problem with 69/70 dash clusters is that the gauges (except ammeter) don't work.  The reason is that one of the various posts of the gauges is touching the metal housing, which basically shorts all of the gauges.  This often happens when one replaces the circuit card.  To solve, take the dash out and loosen the 2 bolts for one of the gauges and re-set the gauge in the housing and re-tighten the bolts.  If you have a multimeter, measure the resistance between any one of the posts and the metal housing of the dash cluster.  If you see 1 or 14 ohms, then one of the bolts is touching.  You will spend a fair amount of time re-setting the gauges until you get a reading of kilo- or mega-ohms: that is the reading you want.
You can't see the issue, as the view is obstructed by the circuit card and the cardboard insulation pad underneath the bolt nuts.

Idle is waaaay too high.  Should be somewhere around 800 rpm; 1600 when cold.

While the engine is running, the only thing the starter solenoid does is provide a connection point between the main harness, battery, and alternator via the large post on the side.  I don't think the starter solenoid is your problem, unless the connection is loose. 

The 8.8 rear end is an entirely different design than the vintage Ford rear that came with first generation Mustangs.  I believe the 8.8 was introduced sometime in the late 70's or early 80's.  It is not at all compatible with the earlier 8" or 9" design.

Sounds like something going on at the fuse box, as radio, backup lights, and blower motor/AC are powered by ACC and fused by 2 fuses.  Might be a bad ignition switch or bad/nearly broken wire for ACC at fuse box.  Usually, it is the BAT line that breaks, not the ACC line.  Something is going on that when more power is pulled through those lines, continuity is lost due to higher resistance.  I'd check your fuse clips first.

Sounds like something going on at the fuse box, as radio, backup lights, and blower motor/AC are powered by ACC and fused by 2 fuses.  Might be a bad ignition switch or bad/nearly broken wire for ACC at fuse box.  Usually, it is the BAT line that breaks, not the ACC line.  Something is going on that when more power is pulled through those lines, continuity is lost due to higher resistance.  I'd check your fuse clips first.

Nope: when you replace the circuit board, you have to loosen the nuts holding the various gauges.  The posts can easily contact the metal housing when reinstalling and tightening the nuts, shorting out the CVR output  and the gauges will not work.  This is a chronic problem for 69/70 dash clusters.  The cheapest solution is to remove the circuit card and place black electrical tape over the rectangular cutout sides so that the posts won't contact the metal housing.  Re-install the cardboard insulation pad, the circuit card, and tighten the nuts. 
As a check, you can measure the resistance between each post and the housing metal.  If you see 1 to 14 ohms, one of the gauges is shorting out, causing the others to short out too.  The ammeter, if shorted, will cause a massive short and because the lines are not fused, can cause a fire.  Bad design by Ford.

You should be seeing 1 ohm or less between chassis ground and the battery ground.  Anything more than that, and you'll begin to have problems.  Ask me how I know...
OK...I'll tell you.  My wife is trying to put me 6 feet underground so I can test continuity to ground...I'm trying to convince her that a copper or steel red/pipe stuck in the ground is just as good but she's not having any of that...

Nope: when you replace the circuit board, you have to loosen the nuts holding the various gauges.  The posts can easily contact the metal housing when reinstalling and tightening the nuts, shorting out the CVR output  and the gauges will not work.  This is a chronic problem for 69/70 dash clusters.  The cheapest solution is to remove the circuit card and place black electrical tape over the rectangular cutout sides so that the posts won't contact the metal housing.  Re-install the cardboard insulation pad, the circuit card, and tighten the nuts. 
As a check, you can measure the resistance between each post and the housing metal.  If you see 1 to 14 ohms, one of the gauges is shorting out, causing the others to short out too.  The ammeter, if shorted, will cause a massive short and because the lines are not fused, can cause a fire.  Bad design by Ford.

Use an export brace to ensure the upper structures of the shock tower are in alignment.

Use an export brace to ensure the upper structures of the shock tower are in alignment.

On my 69 with factory air, the green wire to compressor is molded as part of the bundle where NSS and wiper motor wires come out, about 2 inches inboard of the gas pedal cable.

That's Jenny's CC number. I've got her info saved. 

Damn.  If I had your money, I'd throw mine away!

1970 Standard Dash Cluster Wiring:
 

You pretty much have nailed it.  Easiest, cheapest option is a stand-alone tach.  Would run $60-100.
Aftermarket dash clusters are certainly not plug-n-play, fairly expensive, then add in your labor (or someone else's) to wire it and you're looking an $800+ easy.
There's some jerk named Midlife that can convert underdash harnesses to tach compatible.  But...you'll first need to find a factory tach dash.  Those now run $1000-1500 in good shape.  Add in wiring changes for everything forward of the tail-light and you're looking at another $3-400.
Final option is to sell your car and find another one that already has a tach.  Downside is that you now have a new set of unknown issues to fix...

I like the gloves on the front of the frame rails: looks like they want to grab a beer or two...

With all that spaghetti, be still my heart!