I can tell you that the Fleetwoods (Pace Arrow, Southwind) were steel in that time frame. Can also tell you Holiday Ramblers were alum. Beyond that, I'd just be guessing regarding the ones you're interested in.
The biggest thing I can think of to pass on would be regarding rot and delamination. If you see it, unless you are handy to an extreme, I would walk away from it. Even if you're looking for a project. There are too many available without that kind of trouble.
1997 37' HR Endeavor, 275hp Cat, Freightliner
03 CR-V Blue Ox, Ready Brake