how far can one turn down a crank?

At first glance, if that's my free crank I take it to my machinist and have him grind it to a 4.250 stroke with a Chevy 2.20 journal. Use a 7.100 Chevy rod and a Mopar piston with a .990 pin and about a 1.485 compression height and I'm at 505-512ci.