[Baresteel10]

I have always used these equations to convert crank horsepower to Rear wheel horse power

For an automatic their is a loss of 30% and for a manual its only a 16% loss through the drive train.

Stock I think the 1970 402 found in these trucks had 330 so by multipling that by the loss of 30% from the automatic I was getting 231 RWHP

Crank HP X .70 for the automatic and .84 for the manual = RWHP

The automatic uses up more horsepower because of all the clutches and also the torque converter.

The manual just gets the power straight from the crank granted is still has to pass the flywheel and one clutch it just has less parts to move and less of a reciprocating mass.

I agree with billa on that they use no accessories when they dyno the motors. They use an electric water pump at the most I think and headers. Thats just my .02 cents

PS: The only numbers I am going to care about now are from the timeslips