I may have misread, but you gotta assume the T5 conversion worked at one time which should rule out a problem with wrong parts or the input shaft. So what's left, my vote is clutch disk is rust stuck to the flywheel. To fix that, chain the back of the truck to tree or put the front bumper (at the frame bolt so as not to bend the bumper) then WHILE DEPRESSING the clutch, try and start it in gear. The clutch should slip and break free. If the brakes are in great shape then they may be able to hold the vehicle, negating the need to tie it down of use the bumper. If you go this route, procede at your own risk of course!
Good Luck, RonR
Last edited by moparguy; 07/25/2018 3:53 PM.