4 Wheel Disk on Full size diffs w/ stock Master

OK I am sure someone has done this or at least somthing simular,..

My 1989 Cherokee (MXJ) is getting treated with a D44 HP and a 9", now I have converted both diffs over to mid 80's Chev backing plates and calipers with Fort/Dodge rotors,... My concern is with the stock brake master with the 4 wheel disk conversion,.. Just curious if anyone has done this and what the outcome was,..

Will the stock master cylinder work with the 4 wheel disk? and if not what master cylinder have you guys/gals used?

I'm running 4 wheel discs on waggy 44's and stock MC etc. The pedal is squishy but I can lock up all 4 wheels.

anyone else?

I remember reading about swapping over a grands proportioning valve, since they had discs in the rear.
And also the use of a ford econoline van master cylinder.
search for e350 master cylinder.

I ran a 44/9" combo with discs all around and the stock master cylinder and it did just fine. I never felt the need to upgrade it.

When I converted to 4-wheel discs in my '88 XJ, my pedal dropped significantly upon applying the brakes. If I wasn't careful, I'd push the accelerator at the same time! The stock MC doesn't have sufficient volume to supply fluid to the rears; it was designed to operate the wheel cylinders found in drum brakes, not the volume required for a disc caliper. When I installed my front D44 with Chevy brakes, I found my stock MC wholly deficient in volume. After much research, I chose a master cylinder from a the '76-'79 Mercury Marquis originally equipped for 4-wheel discs and hydro boost.; the cylinder ID is 1.125 versus the stock MC of 15/16. The install was pretty easy, the ports are on the same side of MC as the stock unit, and the fitting sizes were the same, but swapped front to back. You need on new adapter to hook it up. The unit bolts directly to the old booster, using the stock push rod. My pedal is now much higher, and my brakes are good. The pedal is harder and requires more pressure to lock them up. This happens because as you increase the piston size, it requires more foot pressure to move the higher volume fluid.
What I'm looking for now is a dual diaphragm booster that fits the early XJ AND accepts a 1.125 OD piston MC. That would cure the hard pedal issue.

I'm running D60 front and 14 bolt rear w/disc and dual piston calipers up front on stock MC, after bleeding the brakes really good there is just a little bit of low pedal.

I forgot to comment on the proportioning valve. The stock valve, which is a combination valve, meaning it has three functions: a residual pressure valve for the rear drums, which should be removed, or your rear discs will drag, wearing out the inner pads, second a "hold-off" valve for the front discs, to insure the rear drums are applied slightly ahead of the rears, which of course you now don't need, and thirdly, a proportioning valve to reduce pressure to the rear drums so they won't lock up ahead of the fronts. Now you could do what I did, which was to remove various parts from the stock combo valve, effectively "gutting" it, or as suggested previously and install a valve from a Grand Cherokee . This solves the first two issues while maintaining the proportioning valve, which you may need. If you do gut yours or remove it all together, you may need to install an after market adjustable proportioning valve in the rear brake line. You'd know you need to do this if your rears lock up easily ahead of your fronts.