Back story. 1956 Chevy 210 with all stock from factory type brake parts when car was bought in May of 2020 with no brake noise then. Today it has dual master 1" bore pot belly Corvette type master and all new wheels cylinders front and rear. Brake pedal is firm, no air in system, proper rod adjustment. So why the squeak? Could it be that connecting links should be at a true horizontal plain to wheel cylinder like this example... As opposed to this example where links are slightly angled which is how things are on the car currently... It seems (big guess) to me rear shoes are not getting ample force applied leading to squealing. Any other thoughts and things to look for?