nope, like everyone is saying, there are very major differences. you would need a good donor car and basicly have to cut the entire back half off to convert. it would not be just a few pieces. I think the easiest way would be to cut the trunk floor in halfand up the sides after removing the quarters, then cut it at the pillers and welding the whole thing in. keeping it aligned would be a major concern too. but really, otherwize you would be undoing each spotwelded body piece and disecting the sheet metal and transfering it all over. suer big job. but doable.
the elky thing, now that would be even tougher. the wagon tailgate is alot taller, and more then just cut and paste, everything your pasting to is different then the donor, so lineing things up would be real brutal, but again, give a car nut enough motivation and we can do anything.