Huh, figures one of the few things I'm lucky on doesn't necessarily help me, lol. The 340 intake on the 318 heads has got to be an interesting fit, I would dang near put money on it that there was zero machining done to make them match. Probably just looked on the shelf or the nearest junkyard small block for a 4 bbl intake and yanked it. I would doubt the carb is native to the manifold either since it's an electric choke. Can you put a Carter Competition AFB on a Thermoquad bore pattern without an adapter plate?