The frame rails aren't rotting, Im just looking into the future, i Had rot under the passenger rear seat floor boards, (in the compartment where teh jack is and what not right above the muffler, it rotted through the floor, i cut it all out, but the top of the frame rail all the floor board was gone, but the frame rails are still intact and completelty solid,they have surface rust, but im just looking in future terms, woudl it be possible to get this patched or boxed in the future if the rail did rot here, this is the only spot i have rot on the whole underbody,i patched the holes i cut out with stainless sheet metal and caulked it, and painted over the surface rust with rustoleum...so hopefully it stops and doesn't spread...how much would something like that run.... i know i wont get a exact number but about how much? it is a 89, i really woudln't care, but the whole drivetrain has less than 50,000 miles