Brake questions
 

I moved my truck (1972 GMC 2500) yesterday into my new shop space. Truck had been stored a couple of months while I got things sorted out. The brake light came on and the front master cylinder reservoir was dry. I added fluid and got a little brake. I had about a 10 mile drive to the new shop so took back roads and stopped to top off once.

Questions: 1) I can't spot leaks anywhere, could the fluid be going into the booster? 2) I obviously need a master cylinder should I replace the booster too given the trucks age? 3) Who supplies good OEM replacements?I see a lot of "universal" boosters and I just want a GMC one. 4) I noticed a different fluid - water? - beaded up on the top of the brake fluid where would that come from?

Re: Brake questions
 

1) the fluid could go into the booster, but usually, it's the rear reservoir that leaks into the booster, if only one does it, at least as far as I have seen.
2) if the booster works good, I wouldn't worry about changing it, a new booster may make the brakes work worse
4) It could be water, but hard to say without seeing it.