I'll be real curious to know what your solution is. I was having a similar set of problems with my 89, and replaced the master cylinder.  I bled the brakes twice, but may need to do it once more. I've also adjusted the rear brakes twice, and STILL the brakes engage somewhere around half to two thirds down. I'm quite certain my drums are a little bit warped, as the shoes do not scrape continuously, but rather just about once every revolution. I was trying to get the drums off, but what a job!  I pounded the heck out of them with a hammer, plus also backed off the star wheel adjuster about 15 turns, but can't get those things to budge. May try heat next, but put the thing back together for now. I'm told that the distance the pedal travels is directly related to the rear brakes, so I'm puzzled.  And it looks so easy in the video I watched;)

Troy