Vapor lock, I think

[Don C]

If you do a side-by-side comparison of the one from WCCC and the one for the 4350 you will see that are the same. I measured the stud spacing and the throttle bore openings on my CJ Intake manifold and they are the same as the measurements given for the 4350 flange gasket. I'll send a picture of the CJ intake in a few minutes.

 

[RC92234]

If you do a side-by-side comparison of the one from WCCC and the one for the 4350 you will see that are the same. I measured the stud spacing and the throttle bore openings on my CJ Intake manifold and they are the same as the measurements given for the 4350 flange gasket. I'll send a picture of the CJ intake in a few minutes.

Ordered the 4350 gasket. For $7, it won't be a terrible mistake if it doesn't work out..

 

[Don C]

Here is what the manifold carburetor flange looks like:

 

[Stanglover]

I'm just throwing this little extra thing that I did on my 71 intake before I removed the manifold and blocked the exhaust cross-over passages, This might help a bit as it stops the hot gasses getting under the carb base ( that weird looking channel you see in the pic) The holes do not show in Don's photo, but they ought to be there. You can tap those hole for (if I remember) a 5/16" set screw with some exhaust cement. Check!. You NEED to put some grease on the tap so the bits don't get into the motor.
I still use the base gasket with the metal insert, then the fiber spacer and another thin gasket. Of course mine is a square bore, which makes life easier.

 

[1973 Mach-1]

I don't really know how to cross-post one of my older posts, so I just copied and pasted it here. Hope it's of some help.

I just solved a similar problem. I ended up going the long way around the barn for a deceptively simple problem. Here's what I replaced:
First, I thought it was a bad coil, replaced it - No help.
Thought it could be a grounding problem, so I tested the wiring harness to the coil. No help.
Then I checked the plug wires- All good.
Replaced all the plugs- No help.
Then I thought it may be a fuel flow problem & replaced the fuel pump. No help.
Thought the accelerator pump may have had a hole due to ethanol, Replaced first and secondary pump diaphragms- No help.
Was somehow SURE it was fuel related, so I re-routed the fuel line to avoid heat- No help.
Threw up my hands and replaced the carburetor, in desperation. Sadly, no help.
A friend came over and helped me check the timing-It was perfect!
Then he suggested that I replace the coil wire, and I suggested we take a drive to show him how "jukey" it ran and how it stalls.
Offhandedly, he said "Hey, just pull the vacuum advance tubing off of the distributor and we'll take it out and see."

Sunofagun if it wasn't just the vacuum advance!

It suddenly made sense, that it had would miss on low RPMs when under load, and also cut out at around 2300 RPM, when cruising.
I hope you have better troubleshooting luck!