Buick 455 motors, '70 & '71

Recently ran across two Buick Riviera motors, a 70 and a 71, complete,
used, with th400 trannies attached. All brackets and accessories are
still on. Looks like they were just pulled complete and strapped down
to pallets. They turn over by hand and the oil doesn't look bad. I
have a '70 Buick GS455 w/ th400. Was thinking these might be good to
acquire for spare motor/trannie parts. The asking is $75 each for
them. Anyone know about differences or similiarities between the GS
and the Riv 455 motors? Or any differences between '70 and '71? I
seem to remember something about the compression dropping in '71?

Are there any aluminum street heads available yet for the Buick 455's?

2Loose