I'm working on a customer's 1968 mustang with a 302 roller engine in it. It's got Ford racing heads, a single plane intake, new Holley 600 carburetor, new Mallory distributor and protector, new resistor, new coil, new ngk plugs gapped to .042". I can get it running and it runs alright but eventually stalls and won't start again for a few minutes. When it revs to about 4000rpm it backfires through the carb. I'm getting between 110 and 135psi on a compression check with every cylinder being different. After a while it starts smoking as well but not a ton. Hot compression is the same as cold compression, I also tested functionality of the gauge to verify it. It keeps carbon fouling the plugs pretty quickly as well. Any thoughts on this would be great. Thank you.

I'd tinker with the timing and carb jetting.

Sounds like your coils resistance is in correct for the "trigger system" ( points ,CC. magnet, light, etc.) Try the Holly or MSD website,They will explain it all for you.