Brake Booster Version?

[1964FarmFreshC10]

I believe the 4 wheel drum masters were all 1.0" bore for manual and power even into the second gen dual masters.

Originally Posted by theastronaut

What diameter master cylinder did you buy?

Manual brakes generally use a 1" bore.

Power brakes generally use a 1.125" bore.

The pushrod pivot point on the pedal arm also needs to be in the correct location for power vs manual. The stock 64-66 pedal ratio for manual brakes is 6.25:1, power brake ratio needs to be around 4:1 so you'll need to move the pivot point by drilling a new hole farther down on the pedal arm.

If you already have a 1" master cylinder and the pivot point is still in the original manual brake location a booster isn't needed, it'll stop great without it. That's how my '66 is set up, stops great even when towing.