Well crap. I didn't think anything of it, because A) the old MC I pulled off had two different sized reservoirs and B) that was the p/n they pulled up at the parts store. We specified 10" drums, etc. I had no issues with the brakes previously, but I did notice a difference in throw of the piston between the old vs new ones. The piston on the old MC bottomed out about an inch shorter than the new.
Unfortunately I've painted it, so that's $90 down the drain unless I can sell it and recover some cost. Thanks for the info on the Raybestos, I'll head down to the parts store and get it ordered. Luckily, I'm on pretty friendly terms with the fellas there. We'll have a good chuckle when I shame them for steering me wrong.
Yeah, I'm doing brakes now. Long story short, I decided to rebuild the front end while the engine is out, and well, you start taking things apart and noticing more and more things that need replaced/rebuilt. I hope to put this thing to bed in the next couple days so I can get the motor in.