All of the undercarriage is bolt on. Drawbar bolts onto the main sub-frame, suspension bolts onto a cross member, which is bolted to the sub-frame & draw bar. Main sub-frame spars run from the front of the wheel arch to the rear of the floor.
As long as the main sub-frame is still straight, every thing attached would be a "remove, remake, & replace" type of rebuilt.
As for the water damage, there is no timber in them, and all the electrical stuff is up high..so not sure what would be damaged ?
I've not long ago replaced the drawbar on mine with an upgraded design, still have photo's and drawings if anyone was interested ?