I think that a booster is usually used because the disc brakes require a lot more pressure to operate and thus without the booster it requires a greater physical effort. By the way he has disc brakes front and back.

1951 GMC 1 Ton Flatbed -- It is finally on the road and what a great time I have driving it!
1951 1 Ton Completed

My Chevy Master 4 Door is on the Road!