Disc brake conversion (70 Dart)

2nd source on the 6:1 performance advantage comes from Olaf Manthey, Porsche race team owner/driver.

Olaf Manthey: “Removing 33 pounds of unsprung weight at the wheels is equivalent to losing 198 pounds from the body of the car, as a 1:6 factor has to be applied when the car is moving and that weight becomes mass. In fact, we are conservative with the 1:6 ratio, as Porsche considers it to be 1:7"