Welcome to the Stovebolt
Your brake system is a single circuit type, so my recommendation would be to replace/rebuild EVERYTHING including the steel and rubber lines back to new. You don't want to have a failure while pulling your RV.
You also have the 5/10 lug rims so finding usable rims will be challenging. The 22.5" tubeless one-piece rims are the direct replacement for your 20" split rims. There's a good write up on wheels in the "Tech Tips" section.
Mike B
