I can't answer your question on the Silverback but I did install Michelins XPS Ribs on my 318SAB Cougar that I traded in on a new CC34RL this year.
The Cougar had the 6,000 LBS axles and the 16" tires from Dexter Mfg. CO, the axles are the same so the spacing between the axles should be the same also. My tires that I replaced were ST235/80R16 Power Kings and I replaced them with Michelins LT245/75/16 tires. What I did was compare the rolling radius against each other and discovered that there was enough clearance between tires.
I installed them three years ago and was one of the better upgrades to the camper that I did.
Do not forget to have them balance also these are very heavy tires.
2016 34RL CC; 2008 Ram Mega Cab 2500HD, 6.7L, 68RFE 6 speed, 4X4, Smarty S67