2001 f250.starter grinding/not engaging

[jbeasts10]

Anyone had any issues with there starter grinding?I have replaced the starter 6 times,2 new flexplates and even replaced the adapter spacer for the starter.I have installed 3 early model 2 bolt starters,1 denso(one without the adapter ) and 2 late model 3 bolt starters.Almost ready to call it a day and move on.NO end play on the crank.I am not a noobie to engines,I just cant find the issue.Any help would be greatly appreciated