Brian’s stepped up again.
I’ve run the 7.0 class at NPK’s and some other “no prep” events (mostly for the food) with a M&H DOT Musclecar bias ply tire on it just for giggles and giggles is what I got! Really need a true slick for that stuff. These cars really like radial prep because of the stiff sidewall. A low SLR helps to not let the tire get away from you. IIRC, the change to 3.91 was to keep the rpm’s a bit more reasonable.