Be aware that a factory slider fits right up into a gasket that takes the double-wide track and aftermarket sliders (like C.R. Laurence) have a narrow flange that uses the gasket for single pane glass.
A lot has been said about rear gaskets that don't fit well.
There was a thread recently about this.
All this is to say if your factory slider is damaged beyond repair you're going to need a factory slider or a new gasket.
I'm going to link the thread, because there seems to be some confusion about the years that fit. (Up to '81 & '81>)
https://forum.garysgaragemahal.com/Rear-slider-gasket-tp54569.htmlI can only speak for my truck that came with a factory slider, and when I tried to replace it with a CRL aftermarket window I needed to get a different gasket.
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.