GM GVWR/GCWR chassis/powertrain questions

Yeah, that 5 speed sure is enticing but now we're talking $20k+. Finding these class C GM4500 chassis is proving to be a real pain in the ass. I'm having a low percentage of success on my google searches, but I did strike gold on the Ford chassis. pnichols, do you tow with the V10? I see it's around ~300hp depending on the year but over 400# of torque regardless of the year. My concern is how much power is unlocked with bolt-ons on the V10? How durable are the transmissions when you start adding power and beating on them? It takes a lot to push something like that through the wind at altitude with a trailer at 70-75mph (interstate speed limit here is 75mph and trucks don't have a separate limit, I really don't think 60-65 would be a great idea and I doubt I have the patience to go that slow), I don't doubt one bit that near sea level without a trailer that the V10 is more than adequate. I know with the Vortec 454 that if you add a mild cam, headers, intake, and tune you'd easily be ~370hp and 500+ torque (at sea level), but the chassis I find them coming in so far just won't cut it. Of course that 8.1/Allison combo would boogie out with nothing more than a tune, but again we're talking $20k+ and possibly a difficult to find chassis. Maybe not, but I'm still ridiculously new to this. I really like the extras that the E-450 gives on the chassis and it's a bit much to buy a one ton and then upgrade everything on a GM chassis to a 450 equivalent, I don't think the dollars and cents would add up there. Time to hit CL and RVtrader again to research the more expensive rigs and further educate myself on what's out there.