New carb for a 273...

I have a '67 Formula "S" that has the stock 273 Commando. The carb is shot and Im looking to get a new one. I've been eyeballing the Edlebrock Thunder AVS 650, but I can't find ANYTHING that says it's compatable with my engine/ intake! Everything says 318-340... I'm sure that it is, but will I have to change out my manifold (or should I)? Anyone have any insight? I'm open to suggestions on other ways to improve performance as well... (As you can probably tell, I'm pretty much a novice... Here to learn!)