Though I don't have a 3400RL, I did replace my Marabombs with the LT235/85R16 size (see my signature) and they work fine. If I'm not mistaken, you wind up with one inch less between front and rear tires.
I know what you mean about being sick over replacing brand new tires. I just bit the bullet and did what I needed to do to make my rig safe for me, DW and others on the road. Many threads and discussions on this subject on the MOC. Search function is your friend.
LevelUp, Dual 6 volt batteries, Progressive Industries EMS HW50C, Honda EU2000i Generator, Bridgestone Duravis R250 tires, Torklift Glowstep Revolution Stairs, LED Tail lights
2015 RAM 3500 Laramie SRW LB CC Cummins 6.7L Aisin Trans B&W RVK3600