I had to notch the cab and i am sitting like 1/2" so from the ground since there is a cross member that is bolted under the frame. There is also a part near the front of the seats that needs to be trimmed, but you can either get a smaller drive shaft like i did (3.5" D) or cut it out and brace it with flat steel. here is a pic to show how high off the ground and the cab notch:
modded notch from sdoors

laying plated cross member

1/2"-1" from ground this is the rearmost cab mount that you see on the drivers side. the bushing on the right side of the pic is of the 4 link. its exactly where the stock shackle is for the leaf springs.
Now with all that said i have a QC, not sure what is involved with a RC. Could be more, could be less. I know a guy with a BD QC that didn't notch any of the floor for the drive shaft. He simply had a custom 2 piece drive shaft made. And its not weak either, since he uses his truck to tow a boat............