Post us some pictures, and what are your plans/budget. Right way is media blast it and paint it, but right way is $$$$. I am using MasterSeries Silver, like por15 but can be applied over marginally prepared service, we will see. I used a top quality wire wheel on an angle grinder, and I brushed the heck our of the bottom. I also had some sort of 50 year old dealer undercoating I guess. Most of it was already gone, what was left most of that came off with the wire wheel and some elbow grease. If it would not come off I figured leave it as it was good. I then put two coats of the masterSeries silver, no metal cleaner, metal prep etc etc. That is suppose to be acceptable with this product. If it gets scratched this product is suppose to only allow rust in that scratch, it is suppose to prevent the rust from spreading like it would with normal paint. I then put a urethane black chases paint over top of that from the same company. In time we will see if this worked. It was relatively cheap, and it just brushed on with a disposable brush, I sprayed the chassis paint.