Passenger car D 60s have thinner wall tubing than Ford truck D 60s. Floater style Dana axles have very thick wall tubes. All 70s are floaters, so the tubing is very thick. It doesn’t seem to far fetched that a 70 could be 60lbs heavier without axle ends/ brakes.
Comparing images, it looks like a lot of it is in the center section of the housing. Can't see a 70 as a good option for a race car.
If the results don't match the theory, change the theory.
