70 Duster power to manual brake conversion

I do not believe the small leaks you are chasing are the problem I am having the same problem working with wilwood and tring to get in touch with dr diff it could be the 2.6 calipers most people are running the 2.75 calipers cant believe that would make that much difference

I would bet most people are running 2.6" piston calipers. All the stock 73-76 A-body calipers are 2.6's. The only way you'd have 2.75's is if you're using B/E or the F/M/J/R calipers. So you'd have to make a point to get those.

Regardless, that shouldn't cause any problems. The pedal feel would be a little different for a 2.6" piston compared to a 2.75", but both would stop the car just fine and neither should hit the floor if everything is working properly.