Hello, I have 1955 f100 pickup volare front end lincoln rear both disc brakes 8inch power booster gm 1inch dual master cylinder brakes dragging when driving down road come back to shop crack brake line unlocks wheel pressure building some how it is new master cyl which dosen't mean much now days I am tryng to find which stock gm has 1inch cyl with 3/16 ports so i can buy cheap at parts store to try and eliminate m/c I have taken all external valve out of system trying to solve problem there are no collasped hoses Thanks MIchael