Andy, even if you don't want to go the EFI route, I would plan on buying a newer 87 and up 5.0 with the roller valve train, better heads etc. All of the old 302 will fit the 5.0 including intakes and such. The only problem you could run into is that the newer will need an electric fuel pump as the newer motors don't have the knockout where you would hang the mechanical fuel pump and you will need to order a different cam gear for your dizzy.
Not to mention the older 302 from the bronco were only rated at 125 horses and the new 5.0 are 225hp give or take a few. I personally would try to find a 5.0 from and explorer to give you the short serpentine setup and better heads than the mustang. If you are stuck on buying a 302, then it nots really going to much matter at the junkyard in my opinion. Buy something that is stock and that has not been bored and rebuild it the way you want it.
Ben