My enigne is a 502 BBC pushing out 502 HP and 567 TQ. I have 5% gears in the C-500 and am spinning a 12x15 Menkens 3-blade with cup. I am running an ART Carr Turbo 400 with spline drive and reverse manual valve body. I definitely need to upgrade my exhaust but with current set-up and I'm just guessing here as I have not GPS'd it I would say 58-60 mph tops. She turns 4900 rpm at WOT.