I have a '65 Impala frame that I rattle canned about 13 years ago with enamel and the finish remains in quite good condition, no rust (wasn't rusty back then either). Since I'm now doing a suspension rebuild I decided on a urethane upgrade while she's fully disassembled (engine and sheet metal are also removed). Not sure what my prep was back then but since the finish looked quite solid I just took a wire wheel to it and the paint come off relatively easy but a very sturdy red(ish) primer (oxide?, OEM?) underneath remained mostly intact. Figured it's so well adhered why remove more than necessary.

Question now is -- Since wheeling it had me exposing only a few small spots of bare metal should I switch to a urethane primer or remain with my original intent to epoxy it prior to a urethane top coat. I have no need to sand between coats since a non-massaged OEM look is what I'm after. Maybe epoxy for the sealing properties since I'm unsure of the coating that remains? I'm just brainwashed by having heard so many times "epoxy over bare metal only" that I can't help to question epoxy over any other surface despite application labels.

Thanks!