American Powertrain Announces New Pro-Fit 5 & 6-Speed System for 1978 – 1987 GM G Body Vehicles American Powertrain Announces New Pro-Fit 5 & 6-Speed System for 1978 – 1987 GM G Body Vehicles System includes TREMEC® transmission with choice of gear ratios […] Chris Hamilton August 28, 2019 C10 Builders Guide Industry News Latest Product Reviews Tech