There has been some discussion on this here, some saying the glass from all years will interchange, that the opening was changed slightly but will work, etc.
But, as far as my personal knowledge, the glass thickness changed, maybe around the body change, '81, newer glass being thinner.
On my '85, it had a factory slider, with a broken glass when I got it, and I got a solid glass from an '88 to replace it, used the rubber that was around the slider.
I junked the old slider ...
The other day I bought an interior from a '92, and got the factory slider, it has a rubber that protrudes outward to hold the slider, I took it all just in case, but haven't installed it. To me it looks odd, but maybe the reason was to eliminate water leaks?
As far as I know the aftermarket sliders were designed to have the lip same thickness as the factory glass, and would use the original rubber.
I am thinking you need to measure the thickness of the flange, and get the rubber that corresponds, early or late type?
It is possible the slider could have come from a later truck, or the rubber could have, or who knows on these old things.
When you say lip width, do you mean the thickness? Like 3/16" or something?