1966 GMC L4000 Tilt-cab brake parts

[Campbel45]

Hi guys,

I'm hoping to get some help finding brake parts for my gmc L4000 tilt cab. I'm not having any luck with rockauto or napa.

I'm in search of a master cylinder and wheel cylinders. Attached is a few pictures of the SPID and master cylinder. I've got a Chevrolet parts book but I'm not having any luck finding the master cylinder.

This master cylinder seems unique in that the bore for the clutch is smaller than the bore for the brakes.

Thank you for the help.