Aluminum bodies are nice until they start needing repairs. Personally, I'd never own an aluminum body of any kind, work trailer, dump body, service body or whatever. They work harden and can't take the flexing. Once you get a crack in a joint or anywhere it'll be never ending repairs and they are a royal pia to work on as they have to be clean.
I'd be a bit leery also of an aluminum rock body unless you line the bottom with something and then you're defeating the weight savings.
Those are my opinions and they're free so take into account what you paid for them LOL. Good luck on finding a good body, be sure to keep us in the loop.....Mike