Sell my Duster or 360 Swap??? Help?!?

I'd definitely do the swap. Finding any of these cars with a solid body is hard enough, and finding one that's solid and has a running V8 is likely going to cost more than $2,500. That being said, I found my Dart with a 318 and a near perfect CA body for less, but it's got 82k on the clock and a blown head gasket at least, so its not exactly running.

If you really want a V8 soon I'd head down to the wrecking yard and try to find a lowish miles 5.9 (360) and just pull the whole thing. They can be had for pretty cheap. You'd still have to sort out the rest of the driveline, but it'd be a good start.