drum/disc conversion issue

So, I am doing a drum to disc conversion on our 74 Dart. Donor car was a 75 Dart. I have one side sorta on. Went to put cotter pin on the spindle and the rotor assemble doesn't seem to want to go on far enough to be able to get to the cotter pin hole? Wheel bearing is in correctly it spins fine. Put the caliper on and tightened down the back bolts and wheel wont turn at all. What have I done incorrectly here?
Author: admin