Hi, a little clarification on hp numbers. Prior to 1972 hp and torque numbers were measured at the crankshaft with just the bare engine. Beginning in 1972 all hp and torque ratings were measured at the back of the transmission with all options in and operating. These are called SAE net ratings. This caused all hp and torque ratings to drop 60 to 80 hp for a virtually identicle engine as was available in 71. The killer for horsepower and torque actually came in 71 when it was federally mandated that all engines produced be able to run on regular fuel so thus the big compression ratio drop that year. So this said a 71 400 with 300 hp changed to a 220 hp engine in 72 with no real changes to the engine. With these changes a 68 400 making 350 hp in sae net ratings would be closer to 280 hp. So with your engine do you want to add 60 hp or 130 hp?
