I just bought a 70 Mustang PDB setup for my 70 coupe with manual drums. My manual master cylinder is brand new and I would like to use it in place of the old MC that came with the booster. I know this has been asked before and my search of the forum says it can't be done but I would like to know why. My shop manual says both the power and manual MC's in 1970 had 1 inch bores. So what is actually different between the boosters?