Thank you for all the advice. A few more questions: Since there are only a few spots on the back side of the cab that need some minor filler work, would I be safe in removing the primer on those areas, applying filler directly on the metal (I know alot of you suggest putting it over the epoxy primer, that's exactly why I wanted that primer to begin with) then prime over the filler?
Also, the cab was completely blasted inside and out then primed inside and out. Would you take the inside down to bare metal too? Would it really be necessary?