Midlife

Do you have the flickering problem with the light switch in the first detent, known as the park position? If so this would eliminate the headlights and change the search criteria (unless you have multiple shorts).
I also recommend pulling fuse #5, its a 4 amp fuse that controls all these lights: ash tray, heater, radio, 2 clock and 8 dash instrument lights. 

Then pull the light switch to the first detent (park) and see if any of these lights flash: front park lights, tail, side markers and license lamps. Then pull the switch all the way out and turn on the headlights and see if they cause the flashing.

Who was it that said you can't teach old dogs new tricks?

Actually, the Concours Mustang Forum lists all the original hardware specs and platings obtained from various sources.  AMK does a good job for the hobbyist, but if you're interested din which head marking and color is correct, the spreadsheets in that forum is the place to go.  You may have to be a member to get to the spreadsheet;:
 
https://www.concoursmustang.com/forum/index.php?topic=10790.0

I get male/female bullet connectors at delcity.net under trailer connectors.  The 69/70 fuel sending unit uses a standard #8 bolt, and the 90* slip-on connectors that NPD now sells should fit it. 

Actually, the Concours Mustang Forum lists all the original hardware specs and platings obtained from various sources.  AMK does a good job for the hobbyist, but if you're interested din which head marking and color is correct, the spreadsheets in that forum is the place to go.  You may have to be a member to get to the spreadsheet;:
 
https://www.concoursmustang.com/forum/index.php?topic=10790.0

Holy Sheiss!  That's quite a nice collection of 69/70 parts!  The tach dash cluster typically goes for $1000+ on eBay.

If my door is a jar ,i hope it is filled with jalapino stuffed olives ,i like jars of olives !

But it hurts so good. 

Because it's a lot of work, and I'm lazy. True story.

For health reasons, I avoid using any type of Exploding driveshafts. :-)
 

Huh.  Usually, one goes to the bar instead!
 

Just don't get that lizard skin on your hootus. 
https://www.explorerforum.com/forums/threads/how-do-i-get-herculiner-off-of-my-hootus.18595/

I think the appropriate response is: "You Rock!"

Just don't get that lizard skin on your hootus. 
https://www.explorerforum.com/forums/threads/how-do-i-get-herculiner-off-of-my-hootus.18595/

I would also add:
-insurance
sufficient funds in the glove compartment for bribing the local constabulary when caught speeding

That must be a 73 model, when the manufacturers were forced to add 5 mph bumpers!

I got a couple of spare tires, located just above my belt.  Unfortunately, they are not space savers by any definition...*sigh*
Sorry I can't help you further.

I got a couple of spare tires, located just above my belt.  Unfortunately, they are not space savers by any definition...*sigh*
Sorry I can't help you further.

Be careful with opinions...
I had a visit to my doctor and he said I needed drastic surgery.  I doubted it, so I told him I wanted a second opinion.  He said, "OK, your're ugly too"
That is an old but faithful Rodney line. 

Who ever told you that they didn't make Mustang convertibles in 1969 is just odd and should never be listened to seriously.

Who ever told you that they didn't make Mustang convertibles in 1969 is just odd and should never be listened to seriously.

I once had a guy ask me why i had mustang script letters on a challenger / my 69 Mach 1

Who ever told you that they didn't make Mustang convertibles in 1969 is just odd and should never be listened to seriously.

Who ever told you that they didn't make Mustang convertibles in 1969 is just odd and should never be listened to seriously.

Who ever told you that they didn't make Mustang convertibles in 1969 is just odd and should never be listened to seriously.