Do you already have your new front axle for the new build? Have you considered Toyota outers at all? You can run them on a D44 center if you like, then you get 4 piston calipers and 45 degree steering with RCV's.

After you posted all this stuff i started wondering why my setup just worked considering i just randomly put mine together. The Mighty Max has a 15/16" bore BMC, I have the 4 Runner brake upgrade AND Montero rear discs. So i am running twice the calipers and three times the amount of pistons this BMC was designed for BUT as it turns out it's nearly exactly the same setup as the 4 Runner has stock. So i just got lucky that all my mismatched parts just happened to be correct for my application.

I don't suppose you know about the Dodge 1500 BMC crossover? On PA_JERO's rig we are going to run a late 90's early 00's BMC off of the 1500 to power his Wagoneer brakes. He's running Wagoneer front calipers and Montero Sport rears, I imagine we won't be as lucky with this one and will probably go through a series of trials to get it working correctly.
The Dodge BMC is huge and just happens to bolt up to a Mitsu power booster, and Napa has adapter fittings for standard to metric brake lines. I can't remember the bore size for the dodge but we did physically bolt one up to a Montero in the junkyard, there are a few different types though so we had to try a few different Dodges before we found the correct one.