I have an '81 D-150 stepside with a /6, A-833 OD tranny and a 3.54 gear. I is mechanically sound but, it is incredibly slow! I will be swapping it over to a 360 six pack this year. That is the only "SIX" that I want attached to my gas pedal! I figured, why modify the /6 six and still have to listen to that awful 6 cylinder exhaust note...YUCK! Plus the fact that the /6 did not get tremendous gas mileage anyway!