'61 Master cylinder question...

[5Tractorguy]

I'm finally getting around to redoing the brake system in the GMC 5000. I had a question about the master cylinder though and wanted to pick yer brains...

The standard MC for all trucks up to 4000 have a 1-1/8" bore for the brake and clutch cylinder. The 5000 has a 1-1/8" clutch bore and a 1-1/4" brake bore. All the re-manned MC's online and the kits are the 1-1/8" style. The few places I called have the 1-1/8" style.

So it looks like I'll be rebuilding mine unless I can find the correct one. Might bring it somewhere local and see what can be done although I'd rather do it myself.
Anyone got any ideas where to find one? Or the correct rebuild kit? Or have a good one lying around?

Any help is appreciated...