'72 Dart bone stock 318/2bbl upgrade

The eddy intake will definitely fit your stock heads-it's designed for the 273-318 smaller ports. I recall reading an article in Hot Rod a few years ago where they took the 302 heads, cut them for 360 valves, did some portwork and yielded a pretty nice little street engine. I can't recall the power output, but I'm sure a quick google search will yield the results.

My '72 Scamp had the same little 2bbl Carter with the off idle stumble. I just dropped in a 5.2 Magnum out of a '98 Dakota, and thus far the mileage seems no worse with a 4bbl Summit 600cfm vac sec carb (similar to a Holley 4010), so your Holley 600 should work just fine with a little tinkering.

Look up SirDan-he has a later Dart with a '70 front end (IIRC) and he's done much the same thing you're looking at. I believe he went with a 340 cam in his 318 as opposed to the ones you're looking at there, however, the 262 would probably be a good choice.

I'll claim my ignorance with the heads, but IIRC, the J heads would have to be shaved a pretty good bit to get CR back up to around 8.5:1 or so (0.040" rings a bell for some reason) and with that much material removed, your valvetrain geometry would need to be adjusted probably by shorter pushrods...otherwise potential engine damage could occur with non-adj rockers (flat lobes comes to mind-if not p/v clearance).