Here is the link of some POR15 pics including the floor. As stated, prep is everything! To be honest, i didn't prep the floor as aggressively as everything because it will be covered with sound deadening stuff and carpet. I sprayed the metal prep, and then brushed away.Here's a link to my build thread where I primed and painted my frame.....
https://gbodyforum.com/threads/space-city-1982-gp-build.55501/page-5
I know it won't rust for a VERY long time, if ever. Anyways, here ya go.
https://gbodyforum.com/threads/87-cutlass-efi-ls-tt-build-thread-5-11-17.57506/page-5