You will find a plethora of Chevy chassis in the 24 foot size Class C's.
Once you get into the 31 ft size the Ford V10 is the engine of choice.
I wanted a Chevy engine and spent 'months' trying to find a 31ft with a Chevy chassis which is how I came to find out that they where only found in the smaller C's. I've seen a couple of the larger toy hauler Class C's with the Chevy chassis though.