Richmond’s brutally strong 2.43:1 First gear Super T10 presented few interchange problems because the trans mount is in the same location as the mount on the Biscayne’s original three-speed. Super T10s replaced Muncies in the mid-’70s and variants are still used in Winston Cup stockers; they share many features of later-style M21s, including the 26-spline input shaft and larger TH400-style output shaft. The Richmond is about an inch longer than the Biscayne’s three-speed, however, so we had the driveshaft shortened and modified to accept a larger U-joint.