Rams 2018 2500 can have a 6000 or 6200 or 6500 RAWR depending on vehicle selections which can leave the 2500 with approx 2900-3400 lb in the bed payload...also depending on vehicle selections and actual scaled empty truck separate front and rear axle weights.
From this web and other rv webs it seems the 2500 coil spring can carry its rated capacities rather well but the coils don't like top heavy loads like a TC without some mods like the heavier sway bar....HD shocks. More spring capacity if the rear sags however more spring capacity may or may not help with body roll (sway) as with rear coil springs.
I had a '66 chevy 3/4 ton with coils and carried a 8' overhead TC. With OEM suspension body roll was dangerous to the point it wouldn't stop and would actually raise a rear tire and loose traction on wet highways. Gettin' on the brakes would stop the roll. It acted just like a high speed bass boat chine walking......both are dangerous.
The fix was two fold. First was a huge sway bar on the rear which really helped.
What stopped the sway completely was GMs optional 3 leaf over load springs for their coil spring trucks. Coils were a option also.
They looked like a 3 leaf spring set cut in half. They bolted to the trucks main frame rails behind the axle and the other end contacted the axle tube. The spring end that contacted the axle tube had a 3/8" thick hard rubber disc so no metal on metal contact.
I kept the truck for two more years before upgrading to a 9' 6" TC. By that time I had one ton DRW work trucks available.
I would talk with a large Dodge/Ram truck dealer and see if the '18 2500 has any optional equipment to help with coil spring sway issues.
