The frames rust out mostly from the inside out. Where you see the small holes on the inside frame the metal is thin (rusting on the inside). You can do all the clean up and paint you want it will still rust from the inside out. I ended up taking 2 cj8 frames to a shop in Indianapolis In. and had them acid dipped. First frame I painted the inside as well as the outside (sitting in the shop for another build when I finish the cj8 and cj7). By the time I did the second frame I learned more about epoxy primer and shot the inside and outside with epoxy then enamel paint. Reason I learned about the rust from the inside out is I rebuilt the cj7 around 1996 and had the frame sandblasted. Three years later I had the engine pulled and rebuilt by a shop (over the winter). In the spring, I checked out the engine and found he left the jeep sit in a field behind the shop over the winter. 2 years later while doing work under the jeep I saw the holes on the rear, inter frame by the front mount of the rear springs. Ended up doing a complete rebuild including a new frame up restore. With the body/skid plate off you could see the pin holes. Took a hammer to it and once opened you could see how much of the metal was rotted away (and how much was thin and ready to go). In out weather, warm wet ground, cool to cold air causes the moisture to rise from the ground and get trapped under the jeep and condense in the frame. The first frame I had acid dipped I got from a guy in Mi. who sandblasted the frame and welded in patch pieces on the inside of the frame. Looked good but I remembered my first build and played it safe and acid dipped it. When I went to pick it up I found new pin holes where the skid plate mounts (on the inside walls). Ended up plating the inside walls where the pin holes were, knowing the metal was thin throughout the section. I would either cut out the section with the pin holes (don't be surprised if the damage goes a couple inches beyond the pin holes. Then treat the inside of the frame to seal the metal. Sorry for long explanation.