Power Brake Booster for 1970 GTX

Hi. I started out driving and my power brakes worked great, but sometimes the pedal gets hard after I drive it for a while. I can drive it for ten miles or more and it works perfectly. Is there any way to ID to power brake boosters if I need to get one and where is the best place to get one? Also, does anyone know where I can get a check valve? The one I have has two fittings. One fitting to a vacuum gauge. And the gauge says I have thirteen to fourteen lbs. of vacuum. Thanks. I have a 1970 GTX btw.

1970 b-body with disc brakes should have a dual-diaphragm Bendix power brake booster

if you need to replace/repair - your best bet would be having yours rebuilt by: BOOSTER DEWEY

Drum brake w/power use the Midland Ross booster. Vacuum is measured in inches not llbs..

Disc's had the Bendix unit
Ron

Disc or drum matters a lot. For discs, a repop 8" dual diaphram unit is available from Dr Diff.

Are your brakes getting weak after hard use... or just with time running? 10 inches mercury vacuum at idle is marginal for vacuum assist power brakes. Is vacuum getting even weaker when hot maybe? Suggest you check.

Some 70 drum brake cars had bendix boosters.It is not the same as the disc brake one,sorry I don't have a pic of one right now.