My opinion: You own the 500 carb now and know that it works. Since your putting a new cam in the new engine, break everything in with that carb and use it. They are easier to tune than a Holley. (yes for flat out performance a Holley or similar is better) But your post states running around parts chasing fun sport truck...
I will question the 224/230 cam for the 318 though it seems a bit big duration wise for a running around parts chasing fun street sports truck, to me with a stock convertor and 3.23's.......
Sounds like a neat project though Good luck with it!