I cannot specifically help, but here is some info.

As you probably know, coupe/post door glass is different from hardtop glass. I would first try to determine if the new glass you have is for your car or a hardtop. Do you have any part numbers on the glass or from when you bought it?

Chrysler lists different part# glass for '68 compared to '69/70. However the reproduction/aftermarket glass suppliers list the same glass for '68-70 (coupes and hardtops being different). So, perhaps the replacement glass will work.

Hopefully someone with more knowledge of '68 door glass will help you out.

Here is a thread with a photo of '68 post style glass that sounds like you describe.

https://board.moparts.org/ubbthreads/ubbt...terchanges.html


Here are more threads discussing door glass.

https://board.moparts.org/ubbthreads/ubbt...door-glass.html

https://board.moparts.org/ubbthreads/ubbthreads.php/topics/1551534/re-68-gtx-door-glass.html

https://board.moparts.org/ubbthreads/ubbt...-shattered.html

https://board.moparts.org/ubbthreads/ubbthreads.php/topics/146590/re-door-glass-swap.html