GM GVWR/GCWR chassis/powertrain questions

A quick search indicated that E-450 GVWR is 14,500 (vs. 12,500 for most 1 tons, right?). I hate to think it, but would I be better off looking at the Fords? I'm not as familiar with them as I am the Chevies with respect to the powertrain. On the Chevies, I know if I get a TBI 454 I can slap a Vortec top end on, convert it to OBDII, and tune it myself. I'm not aware of what I can do to a V10 for power aside from headers and a tune, nor am I familiar with the transmssion they came with (E4OD?) or how much abuse they take. I've read good things about the Ford's powertrain in stock form, but the fear of spitting a spark plug makes me uneasy. With a GCWR of 20,000# on the E-450 and rated to pull a 10,000# trailer, optional diesel engine but it's the 6.0 that like to blow head gaskets and turbochargers. I guess now I research MH lengths and wheelbases to get a better idea of the Fords.

Edit: decided to put this link in here, some good techy info on E-350 vs. E-450.

http://www.rv.net/forum/index.cfm/fuseaction/thread/tid/19501818/print/true.cfm

Another good read, kind of explains why I'm having a difficult time finding a chassis with a lot leftover.

http://www.rv.net/forum/index.cfm/fuseaction/thread/tid/26387249/srt/pa/pging/1/page/2.cfm

Chassis overkill pretty much sums up what I'm after, but it seems I'd need to buy newer to get it. . .