What a bust...

Rear springs are the same width for all a-bodies, but the 8.25 and 8.75 axles have bigger axles tubes, so you will need to grab the lower shock mounts and u-bolts (if you can get them off without cutting them). At the very least grab the shock mounts with the rearend, I've seen those go for a pretty penny before and it would suck to not be able to swap the axle because you don't have the cash to buy the parts you left hanging on the car.

Driveshaft length is an unknown for me as I don't know what car it would be going into.

Even if you aren't interested in making a couple of bucks, you need to grab those parts. Can't tell you how many people I have seen post WTB threads for parts just like that, hate to see them get crushed.