To be clear, you problem is the clutch will not disengage, correct?
This seems to pop up a lot, aftermarket masters tend to have slightly shorter pushrods, also I've seen the hole in the pedal elongate after 40 years of hard use. Look for play at the hole in the pedal if there is none, and your clevis is adjusted all the way out yet not preloading the TO bearing you might simply need a longer pushrod or longer clevis. Just be sure you have it adjusted with no preload on the to bearing, if the to bearing is pushing on the tines of the PP while at rest you'll burn up that clutch in no time. Less likely but I've had bad pp's that were way way too stiff.