Adding a brake booster?

I am going to 'upgrade' (albeit slightly) the small-bolt discs on '70 Dart to the single-piston setup from '74 Duster. Main reason is to acquire the larger stud 4.5" pattern. I could use the removed parts (from Dart) to install on '69 Valiant, however, the (four-piston) calipers in bad shape - so no good even for cores. Rather than purchase (pricey) new or rebuilds, I will, for now, leave the 9-inch drums intact and add power-assist. Can I use the Dart booster and what M.C.? Will the inlet area of the booster 'interface' with the pedal linkage under the dash? Any tips are appreciated. Note: Valiant stored for winter to at least end of Feb.