I used this disc brake kit
http://mbmbrakes.com/1964-1972-gm-a-...c-booster-kit/ and I'd be willing to bet this is the same kit or very similiar to what right stuff sells, I have both the SPC uppers and lowers and have zero fitment issues on my 65 LeMans not sure if a drop spindle would throw a wrench into anything? Only issue so far is that I used the longer link on the front side of the upper and have over 7° of caster and they couldn't get the -.5 of camber set, going to swap the links and get it aligned again.