I have a 97 GMC 1500 keeps going through starters change flywheel wiring harness crank position sensor wondering why

What symptoms does the starter show before failing? Slow to turn over engine? Premature failure? What engine do you have? (ie high compression?) Is it wear or electrical failure? If it's wear, make sure the starter is properly shimmed (symptoms may include starter doesn't engage or disengage properly). If it's electrical, make sure it is properly grounded.

When I first put the starter in the truck starts really good then it starts after about ten or fifteen cranks it starts grinding again I've tried shaming I'm sharing one side or the other side I've done check my flywheel so I will look good someone said that the motor has been changed in it and that my computer could be in hard mode is that true

If the motor has been changed could it cause a problem like that without resetting the computer

Yes it could, the ECU needs to match the engine specs if not that can be a problem.