my manual brake experience

jduster if your manuals don't stop they are just not set up right. Not the right parts combo, or if drums, maybe the shoes are poor lining or not arced to the drums, etc. Poor choice of wheel cylinder/ master size, etc.

"Generally" larger wheel cylinders/ or smaller master gives you more "lockup" force with less pedal effort but longer pedal travel. Of course the system must be bled, and the pedal should be "rock hard" if so.

Drums--The larger the drums are turned, the worse the shoe diameter fits, and they must be "arced" to the drum diameter. "Good luck" finding a shop with an arcing machine.

If disc, look for odd wear on the pads indicating misalignment between pads/ calipers and disks. Disks must be properly turned and finished to relieve wear patterns Shoe and pad type make a big difference.

When my car was running I had the LOLOL stock drum master with the residual valves disabled, 73 A body disk conversion front, and Ford/ 9" Versailles rear discs. My legs are not that strong anymore. It does require a little push, but you could lock them up no problem. The Dart would easily out-stop the much hated 95 Olds I had at the time.