BIG A#$ Brakes dilemma..

[MadRatt]

Hello everyone,

So I just picked up a 1984 C20 that used to be an old railroad truck. You know the ones that actually drive on the rails. (and no it doesn't still have the train wheel things on it. lol) But it does still have the inverted or reversed 19.5 steel wheels that narrow the width so the tires match the rail width.

So here is my dilemma. It has MONSTER brakes on it. The front disk's are 13" and the rear drums are 15"

It has no brake pedal pressure. I believe the master is shot. I pulled it off and it has a 1.5" bore on it. The spid has no code for brakes or even a listing of the brakes. I thought it would be the JB7 or JD7 but that only has a 1.25" bore. It is a cast iron master with the small chamber in the rear of it. It has a pretty big booster on it so i'm thinking that this is some special combo that was maybe converted by the rail company or ordered that way but not listed. I don't want to just throw a new style 1.5" bore plastic style on it and have it not work proper. Or just get a new booster and master from a JD7 and it not be enough for this Huge combo. Any suggestions as to how I would look up a master by bore size and see if I can match it? I've been all over the net to no avail. Maybe one of you guys has come across this before.
Any help would be appreciated.