That diff has a snowflakes chance of surviving behind your Mitsi Motor. Andrew Dennis (ca18det_man) used a Mitsubishi diff in his 1200, I think it was from a Sigma Scorpion. you could probably find his old build story. Or you could do a Hilux diff, or a Gazelle H190 with modern offset wheels. That photo of the sill with the paper poking out reminds me of my first 1200 coupe, that had both sills made of newspaper & body putty. I got some new sills made from gal in a thicker guage & replaced them. Made the car much nicer (& safer) to drive.