Like Nike says: "Just Do It."
You don't give a chassis make or year so I'll assume Ford E-450. Do you have sway bars now? If so measure them and compare the size to what is listed for your chassis on Leaf Springs, Helper Springs and Suspension Parts | SD Truck Springs
. I think you will find they have about the best prices. Get the biggest ones you can find. IMO don't bother spending the money for Roadmaster. They are no larger unless something has changed.
Installing larger bars will make a dramatic difference. How are the shocks and the rest of the front end parts? Also, do an axle weigh and make sure you are running air pressure according to the tire manufacture air inflation charts. When you get done with the install have an alignment done by a shop that understands motorhomes. Assuming a E-450 ask them to get as close to +5 camber as they can.
I replaced mine on a 2007 E-450 under a Sunseeker 2860. You can DIY with basic hand tools in a day. That included a long lunch break and a couple of beer breaks.