The oddball master with the small fittings is likely for FWD.
For reference, I have a 69 Roadrunner with the Cordoba ft brakes, 10 inch drums no assist, 1.125 aluminum 2 bolt master. Wheel cylinder are too small but car stops quite well.
Regarding fluid flow when bench bleeding, it doesn't matter. Once both sides are bled out they function in tandem with a possible miniscule difference where the port closest to the pedal will flow first. This is basically from the slack as the seals expand etc.
Caliper bores are going to be needed, see Feets thread on brake math.
What are you using for a proportion valve? A properly balanced all disc system shouldn't need one.
On the hydroboost I wonder if you had the lines reversed.
Your car stops well because the drums at the rear require little pressure to operate and they are "self energizing". When I had a disc-drum arrangement, my car stopped about the same as when I changed to the 11.7" rear discs. I didn't expect much of an improvement anyway, I wanted the improved appearance of the disc rotor.
The caliper bores are Front : 2 pistons @ 1.59" Rear: 1 piston @ 1.50".
The front to rear bias matches a 1994-2001 Mustang Cobra as stated by Dr Diff. The bias matches the 2 to 1 goal which is what Andy Finkbeiner says is the desirable target.
There is no proportioning valve. The lines all merge into a drum-drum distribution block which has no proportioning factor to it.
The hydroboost was plumbed correctly. There were no mistakes there. Apparently, the bleed process can take quite a while or it can bleed fast. It can vary. Some HB units require more pressure and volume than a standard pump can produce. I used Saginaw pumps because that is what was on the car, the brackets I have fit the Saginaw units and they are OEM in Chevy trucks with hydroboost.
