Update: I finally got my brakes sorted out.
As noted above I was really leaning towards rebuilding my Midland booster, getting parts for it was just not working out. Lead times were crazy long or the price was crazy high. Went back to original plan of rebuilding the Bendix.
I got a rebuild kit installed and everything seemed well and good - except that same as before - installed on truck and brakes are on full stop.
I ended up having a few diaphragms for the control body and decided to shorten the rod that inserts into the control valve cylinder. Deciphering the wizardry inside the control valve well enough to type how I decided to do this is beyond me - but it DID WORK. Brakes are working like they should.
Other thoughts, I do think the Midland had a better pedal feel, maybe it produced more boost. Also ran a new hydraulic line from master cylinder to booster with new double flare fittings.
