Did you open the brake hydraulic system? If so, how did you bleed the brakes? If you used the "pump the pedal" method there is a good chance that the master cylinder is shot. Even if you didn't open the system moving the master cylinder piston though an area in the bore that hasn't been used in almost 20 years can rip the seals. You might get buy with a seal kit(for the whole thing, not a single seal)but if it had enough corrosion or build-up to tear a seal...just replace it.
Regards,
Randy D.