What is the max that you can bore out a stock 502 MPI?

4.600, but you need to sonic check the cylinders for thickness to be sure the core shift isn't to bad.

Gen V or VI 4.530 is my limit 4.600 in the bottom cam side won't leave any material except a sharp edge.

I am not a engine builder. But when you say max, do you mean "RELIABLE MARINE ENGINE BORE" or fill it with concrete at the race track bore. I have always been told 60 over, I had mine bored 30 over in case I needed another rebuild. If you want more CI stroke it.