Low Pedal

70 Challenger notice break pedal going further down then normal. adjusted break and same. Front part of master cylinder was out of fluid. Does that mean I only have to bleed front Breaks ? Stock break and master . .
thanks
'Gregg

yup

but won't hurt to bleed brakes all around to be sure.

and inspect lines, etc, to see where that fluid went/is leaking.

Front reservoir feeds the REAR brakes.

Fix the leak.

If you can't find an obvious leak, check the MC/booster.. I have seen the booster suck brake fluid.....

And the rear shoes might be all worn away, so check that.

Theoretically, the self adjuster should compensate for worn shoes, if it's not, fix it.

I'll guess rear cylinders are leaking

As said, find/fix the leak in the rear brake half of the system (MC/wheel cyl/lines) then bleed the MC then bleed the rear drums.

Just have 100 miles on it from a 15 year restore. Don't see any leaks guess have to pull the back drums off.

It may be possible that whomever bled the brakes failed to fill the reservoir after doing so. A quick drum pull will confirm if you have leaky cylinders,