73’ 318 dies under accel with new intake & carb

Yep, that's what I said, and I stand by it.
I didn't say you ALWAYS use ported vac, it depends how you set up your engine, what ignition you're running and how you dial it in.
His is bone stock. Using manifold vacuum in this case WILL make it bog.
What I DID recommend is that he use ported vacuum because that is what the factory used, and he didn't change a SINGLE other thing other than the manifold and carburetor. His ignition is set up to run ported, and unless he changes a bunch of other things that I won't get into here (because it's not relevant to his issue), it won't perform properly.
Now, there could be other issues contributing to the problem, as others have pointed out- but it's certainly a contributing factor in his case.
My son and I were troubleshooting a problem with his 360 truck. We found the vacuum canister diaphragm was ruptured, and he was using full manifold vacuum. We replaced the canister, set it for the timed spark port, then retimed the dist. Difference in performance was amazing. Also, seems to me if using the full manifold vacuum and the engine backfires hard that could cause a ruptured VC?