Start here: .
https://forum.garysgaragemahal.com/1980-81-sliding-door-lock-project-tp89331p147918.html
Jim,
Lil'Red is a '87 F250 HD, 4.10's, 1356 4x4, Zf-5, 3G, PMGR, Saginaw PS, desmogged with a Holley 80508 and Performer intake.
Too much other stuff to mention.