Need advice on my 318

I'm getting this engine with a 904 tranny for $300, so buying a different engine isn't going to be cheaper. Regarding headers, my car is a 66 dart so the only reliable source is TTI to the tune of $850....I'm going with manifolds to save money.

Locally a guy is selling a week rock performer for a 318 that requires a square bore carb. Not sure what that means but if I can get it for $50 maybe that's the way to go