DO NOT use the carb base in the equation. The only reason "carb base" has been mentioned is because most are cut at a 3 degree, angle so the assumption is the engine crank centerline has a 3 degree down angle. The simple fact is you want to measure and adjust the relationship between the crank centerline (trans output shaft) and the pinion. - with the weight of the car on its wheels so that the rear end is at ride height.
YES! THIS ^^^ . DO NOT rely on what you think the motor position is to set the pinion angle. Measure everything where the ends of the drive shaft connect to the transmission and the rear end.
Take one set of degrees off the flat end of the transmission tail shaft (not the transmission housing, the actual shaft the drive shaft yoke slides over) .and the other measurement off the the pinion shaft (the yoke the drive shaft bolts to is good enough as long as you use the machined surfaces where the U joint bearing caps are bolted in.
