GM GVWR/GCWR chassis/powertrain questions

Alright, now I feel a bit more edumucated and better armed since I don't need to search for something that doesn't exist. Curb weights are what will kill me though, not knowing how much is "leftover" on a given unit I might check out. Are there any MH in particular to watch for that have a little leftover (besides the smallest E-450 I can get my hands on)? My thought was if the 22' MHs have the same GVWR as the 25 footers, I'd have a little more wiggle room, right? Or are their GVWRs conveniently lower as well as a lot have small blocks? It's becoming more and more obvious that MH manufacturers try to get the cheapest chassis possible and load it as full as possible of goodies since that's what sells, can't really blame them. Should I be looking at class A's too? I'm shocked on some of those at just how much camper they'll put on top of a gas engine.

EDIT: In search for GVWRs, I came across this. The hood looks funny, so I wonder if it's the 94-96 body style you mentioned despite its short wheelbase.

http://www.commercialtrucktrader.com/find/listing/CHEVROLET-G30-109030842