RA81 destruction

I'm not one that ever advocates tearing apart classic gear. But in this case I think it's warranted and I'd like some advice. I have more than a few RA81's that are all clearly labled "BAD HDA", and the person I got them from confirmed "these are all dead". I grabbed them anyways as they had to be taken as part of "the deal". I am not familiar with these drives at all. From what I've heard over the years, they have a fairly high failure rate and thus people who use them are often looking for HDA assemblies. This makes me think that it's unlikely that I'll be able to just pull the bad HDA's out and obtain good ones to put in. Plus I don't need this many drives at all, so I think it's time to tear them apart and scrap them. Since I don't know anything about RA81's yet (have never used them or opened one up), and because I do intend to keep one or two of the drives running (a few don't say "bad hda" on them), can someone tell me what parts I should scavange off the dead ones that are worth keeping as spares? I know the obvious like the light bulbs and drive select plugs, but what about components on the inside that "those in the know" would advise I not just pitch with the drives? Lastly, are the casings for the RA81's mostly steel, or aluminum? I'm pondering putting them in the van and taking to a scrap metal dealer. I wouldn't do this, but they are clearly dead, HDA's not likely to appear, no one wants them, and I need the space. Jay West