Can’t get it to idle

[chvet73 0]

My 1970 302 originally a 2bbl will not idle. It will only run by holding about 2000 RPM. And then it sounds awful.
Now let me explain its history and what has been done. The car has at least 125,000 miles and may well be 225,000. It had a leaky water pump. So I changed it. While apart I did check the timing chain and marks, it looked OK. As old as it is it did run OK.
Then a few weeks later I discovered a large amount of coolant leaking from the intake manifold. When I bought the car it came with a brand new Edelbrock Performer RPM manifold and a 1406 carb. Although I planned to do that change later on, I decided that I might as well do that now to cure the leak. 
So I went ahead with the installation. I has never run right since.
Here are the things I have done to correct this:
1, Removed and reinstalled the manifold twice using Felpro gaskets and changing to Mr. Gasket. I also added ARP studs on the last install.
2. Used 2 different distributors, the original and a brand new Pertronix. Reinstalled both multiple times.
3. The car has an MSD 6A. So I removed that. It was running fine with it before the manifold change.
4. Used a Holley 600CFM carb to replace the Edelbrock. Rebuilt both carbs.
5. Tried both the original and an electric fuel pump.
6. Tried 2 different fuel filters,
7. Tested for a vacuum leak and found nothing. This was hard to do at the 2000 + RPM.
8. Ran compression test. Although a cold test as it’s hard to get it warmed up. No cylinder is less than 155 and consistent 155-160 across all. 
I’m suspicious of the plug wires. They are MSD and were on the car when I got it 2 years ago. I once had a car that I put brand new Accel wires on and it had a high speed miss. One night I opened the hood before I turned on the garage light. The wires were like a light show. Replaced them with Taylor wires and never had an issue in the 16 years I kept that car.
Just a word about my own background, I’ve been working on cars for over 50 years and have never encountered anything like this. 
So I’m at a loss what to try next. So I’m open to suggestions. 
Thanks in advance

[Brian Conway 255]

Relaced everything twice except the intake manifold? Could the problem be with the Edelbrock? Re-check the firing order and plug wires? Check by Pulling plug wires? I realize if you can't get it to idle this can be difficult. As a last resort ask a friend to double check your trouble shooting efforts. Brian

[Mach1 Driver 528]

This video may be helpful:

This is an excellent tutorial of how to install an intake manifold:

Mustang Steve: https://mustangsteve.com/how-to-install-an-intake-manifold-on-ford-289-302-and-351w-engines/

[chvet73 0]

I have checked the firing order and it is correct.  

[Brian Conway 255]

OK then you say you haves changed everything at least once.  Leaves only the plug wires?  Check for continuity?

[aslanefe 320]

You have a big leak under your carb, spraying something to find a leak does not work for a big leak. Check the gaskets and the spacer under the carb. Years ago when I bought one of my cars, it had the same problem; only ran at above 2000 rpm, if you lowered the idle it died. Can't remember exactly if the spacer under the carb was flipped upside down or the gaskets under and above the spacer was wrong which caused a big leak.

[chvet73 0]

I have checked the firing order and it is correct.  

[chvet73 0]

I have changed the carb gasket 3 times. There is no spacer.  

[aslanefe 320]

11 hours ago, chvet73 said:

I have changed the carb gasket 3 times. There is no spacer.  

Running high rpm is a leak, not related to ignition, timing, fuel filter, fuel pump, compression etc. You have a leak between cylinder heads and carb. Did you try putting on the intake and carb the car came with? Did the car have a spacer under carb before you changed the intake and carb?

[chvet73 0]

No I have not gone back to the original. But the original 2bbl did have a spacer