91 mustang brakes
 

i took my brake booster off my car bought the adapter plate to bolt the master cylinder back in stock location. but my problem is after i bleed the brakes the front brakes work fine the rears is like there is nothing there and i did leave the drum brakes on the rear and i have went through a gallon of brake fluid bleeding the rear i dont think i have air in the line so what do i do? i still have brakes hooked up through stock proportining valve

Welcome, are the back shoes adjusted up to where they just touch the drums?

yes the rear drums are adjusted