Gene my assumption is that the frame is solid and rust free, I have been out here in CA a long time and I dont see much rust your right, if the frame is weak or rusted, I would defiantly build one from scratch.
by the looks of the body I figured that the frame would be in good shape.
I don't know how much Steve can do himself or what friends can help him with this project.
I just figured going with the original frame would be an easier way to go, building one from scratch is a good idea too just a little more costly.

Ive done cars both ways, scratch built and putting stuff on stock frames with good results. I just figured if he went with the stock frame he wouldn't have to mess with body mounts Ron....