I use POR15 inside my engines as well. BUT the casting finish gives it 'teeth' to keep it in place during heat cycles and vibrations. Unless that pan was sandblasted even POR15 could theoretically flake off over time and use.
Do like RK advised and do the scrape and scratch test.
Yeah, even a Krylon rebuild doesn't give those worn out bearings another 50K miles ! :shock: :shock: