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Are rear brake shoes adjusted out to almost grabbing when rotating drums as this can make the difference of "getting pedal" in the first few strokes thus resulting pressure for bleeding system.
Bench bleed again if Master on the car then "with pedal", add lines and top up fluid then w/ all bleeders confirmed closed, burp Right Rear first then LR rear then RF and LF last.
As above, two guys work best, especially when troublesome systems as sometimes guy one needs to pump/pump/pump for pedal then guy two immediately release/bleed and quickly tighten...then back to guy one and repeat all a few times in a row until firm pedal achieved.
Make sure fluid level up after each corner burped and good luck!
~ Pete
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