I cut out the end section where the old door latch was mounted and fabricated a new piece out of .060 steel to work with the 06 latch. The only thing I wasn't to happy about is there will be a small break in the door seal rubber because of the way this one engages.
After the door side was taken care of I mounted the latch so that I could do an alignment with the door jamb.
I cut out the old jamb as the latch area was too deep to work with the new catch.
I made a filler plate out of .060 steel and modified the floating backer plate that was in the 68 door jamb so as to have a way to adjust the door catch.
I then mounted the catch and adjusted it so that it would line up in and out as well as up and down.
After the catch mechanism was operating correctly I cut out the section of the inner door panel from the 06 to help locate the inner door handle.
I welded a piece of 1/8" x 2" steel strap on the back side , drilled and tapped it to secure the handle.
I took the 06 actuator rods for both the lock button and the inner door handle and modified (mostly straightened) them to work in the 68 door.
The thing is I committed to the location of the latch before I checked the rear glass track and it just missed by a whisker. Sometimes it is better to be lucky than smart.