[dsraven]

if you end up getting under it also check the release fork and pivot ball for wear or damage.
with a truck that clean it may have been pressure washed even up inside the bellhousing, getting rid of any lube that would be on the release fork ball etc. the visual check doesn't take long, gives a good idea of how much lining is left (if you know where to look) and if it looks good then possibly cut a length of lumber to wedge the pedal down and try that. if problems persist then it looks like tear down time. really, with an open driveline, the right tools and a place to work, thats a quick job.