Super C is a trademark for one brand of RV, and they went out of business a few years ago.
Are you looking for a RV based on the GM 5500 series chassis? With the 8.1L gas engine or the 6.6L diesel? GM stopped making that chassis a few years ago, and stopped making all motorhome chassis back in 2012 or 13.
There are a few designers that build on a F-650 chassis, and a few more that build on the F-550 pickup chassis. The F-550 is the only one I know of that is both with a 17,000+ GVWR and 4 wheel drive! You might be able to get the F-650 and F-750 in 4 wheel drive, I know they offered it for many years.
Check out the 'toyhauler' area, and they list several manufactures, some offer a F-550 based motorhome that can be bought as a toyhauler with a lift in the back to bring toys into the garage area, and they also make traditional class C based on the F-550 chassis, that can have a 19,500 GVWR or the lighter version, 17,000 GVWR! That is pretty heavy duty!
Haulmark is a excellent brand. If you find one less than 3 years old, expect to pay more than $100,000 for it!
Heartland RV is making F-550 based RV's and I am not sure who else is. . .
Good luck,
Have fun shopping!
Fred.
