First, Here's a couple pictures of the differences:
stripped the door that i'm using down to the shell:
For the pattern, i just cut some poster board in a shape that I thought would be an easy cut. I also made sure it would cover the latch location, and screw holes on both doors. Once i had it the way i wanted it, i outlined it on both doors:
Here are some pictures of the measurements I made to make sure i put the patch in the right spot:
Here is the patch cut out of the donor door. I cleaned it up in the blast cabinet, filled the holes from where i removed the spot weld where the bracket were in the donor door. (the earlier doors didn't have that bracket). then I sprayed some weld through primer on the inside part of the patch to keep it from rusting until i coat the inside of the door.
Then i set it in place of the early door and took some measure measurements to make sure it looked good then i cut it out and cleaned the edges for welding
After I was sure it looked good, i set the patch in place, tacked it in, took some more measurements, then welded and grinded the welds down.
Then i put the latch in and remeasured to make sure it was in the right position. Turned out perfect... (you can scroll up and check the original measurements):
