I run a Dynamic 9.5 converter that will flash about 4200 at the track. And I use 4.30's with a 30" tall tire. I will say it drives great with that converter as it has no slippage driving around even on back roads at 2000 rpm and in that area. I honestly feel like my car may go faster with less gear as I trap about 6400 and it pulls real hard from 5000 to 6200. I just don't think I need that much gear with my 493 eng. I would be very curious to see how the converter works and drives with say 3.91's in the car as the converter was actually built for my old 440 and I just put it back in behind the 493 and it has worked nicely. I really hope to maybe swap in a 3.91 or 3.73 pumkin into my 8-3/4 rear and try it. But I will say I really like how nice the Dynamic converter works and how it drives so nice even at lower rpm's without it sounding like it has any slippage to me. Good luck with yours , Ron