318 2bbl manifold swap with OE cam - worth it?

The carb and intake you have in mind will work great on a mild 318. Since you will have the intake off, I would replace the cam. My reasoning would be that the original timing chain and cam sprocket are probably still in there and WILL fail at some point regardless of the carb. The XE262 or a stock 340 cam will work well.

Sure, the cast iron exhaust manifolds will hold you back a little, and if you are still running single exhaust, FIX THAT FIRST before the carb.