M-2300-G rear brake Squealing!!

[67w30]

Third set of rotors and pads, brake squealing won't go away!!!!

So to start this off I'd like to share my info: 67 Olds 442 front Tall Spindle conversion with 12in rotors and 9in rear with Explorer rear disc conversion

I have used both the original disc/drum, mid 70's 1in bore and 1 1/8 bore disc/disc master cylinders to a disc/disc prop valve with a wilwood adj prop valve in the rear 1/4 brake line. Double/triple checked a 2.5 brake gap as required.

I have swapped out all three m/c and no luck, adjusted the wilwood valve and no luck, cleaned and lubed and replaced the rear rotors n pads with no luck!
I am currently running the original disc/drum m/c, disc/disc prop valve (basically a distribution block now), wilwood adj valve shut all the way (restricts 55% braking force/pressure) and I still have the rear brake squealing!!!
HELP!!!