adding a proform main body to a 650 dp

A larger carb has a weaker signal, so picking the "right size" is key, it has everything to do with both air/gas, they work together, more CFM means more gas unless you don't want it to function propperly, In my opinion, the 650dp is all you need for a 318 combo like yours, now for the lower cost of the PF MB kit, i'd say get it & try it, if you don't like it switch back & in the future you'll always have it if you ever upgrade to a different build, i ran 12.5s all day on my 360 magnum in a dart running a 650dp.

If you do this, please make sure you follow the directions carefully, the supplied airbleeds need to be currect from a 2 corner too 4 corner idle carb, they should come with 2 .036" bleeds & 2 .075" bleeds, If you only have front mix screws you need to make shure the .036s are installed on the rear outers of the mainbody.