If you're looking for a non-epoxy primer that has held-up on a Stock Car I painted 6-years ago (and has been left outside all smashed-up for the last 5)...
My jobber used to carry Benjamin Moore "Implement" paints and primers in addition to the DuPonts I always shot. I used the grey implement primer (like the stuff farmers would use) on frame and interior of the stock car, and used DuPont (don't remember which model at the time, but I know it wasn't Prime&Sand) on the sheetmetal.
I don't know if BM still sells that line of Implement primer, but it sprayed well, dried well, but was almost rubbery after dried (absolutely SUCKED to try and sand any runs).
Now, 5-years later, the twisted-up frame, engine-compartment, and interior look like I just sprayed it, and the DuPont sheetmetal actually has rust-holes!