How tall are your tires? looks like you need a little more rear gear. My 73 with 7.5 comp E-58 ran 14.3 at 95.5 and it weighs the same with 3.91s The Turbo action man valve bodys all were fast shifting but very hard on drive train U joints etc. Went with full automatic valve body using Darrell Young mods and never looked back. Car with shift fast and firm 24 years after it was built with 30K or more on trans car is faster in drive and shifts can be set for 5300 or 5700 in drive