A pretty close estimate can be done without pulling the pan. Mount a dial indicator on the lower part of the bellhousing with the stem on the flywheel, and pry the harmonic balancer forward and the flywheel back. The movement of the dial needle will be the end play of the thrust faces.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!