Affordable 15/16" manual master cylinder to fit a first-gen F-body???

[atomicjoe23]

I'm upgrading the front brakes on my '67 Firebird 400 coupe (manual brakes) to the Kore3 GMSS C5/C6 325mm kit and I need to install a new master cylinder as well; I would like to run a 15/16" master cylinder after talking with Tobin via email. . .

. . .problem is, I don't want to spend a couple hundred bucks on a master cylinder that I'm not going to use anymore once I get around to upgrading the rear brakes. I'm not planning on upgrading the rear brakes until I upgrade the rear axle though. I don't wanna buy a BOP rear big brake kit from Kore3 only to have to replace most of it when I swap the rear end out for a 9".

Does anyone know of an OEM 15/16" bore master cylinder that has a bolt pattern to fit a first-gen F-body???

Thanks!