I agree with Doc completely. The only added benefits of a transplant is parts availability locally and you end up with more power, but a complete transplant for $1500 isn't likely considering all the costs. I don't know why AX thinks there is more maintenance on a flatty, that has not been my experience. If yours is leaking (antifreeze? oil?) a $100 worth of gaskets will fix that. Any 302 you get for the money you've described is likely to be leaking, and an AOD that old is going to be a crap-shoot as far as needing a $1200 rebuild.

Whichever you choose, it will make a huge difference in your truck!