Vacuum Booster or Not?

I had original Kelsey-Hayes disc brakes on my '70 Duster that were manual and I liked it a lot. You definitely have to press harder than power brakes but the increased "feel" in the pedal is great. Really helps in low-traction situations (ice, etc.). I never felt like I needed more brakes either, I had enough stopping power to haul down from high speeds just as easily as any newer car. In fact I'm upgrading to '73-up disc brakes and I'll be keeping them manual.

Only crappy thing is heat buildup and fade, try to run wheels that ventilate the brakes. I had factory steel wheels and the brakes would get noticeably weaker after lots of stopping.

BTW if you want a big improvement in braking power get an adjustable proportioning valve; from the factory the rear wheels lock up WAY too easily and the fronts end up getting too little pressure before then.