I have a '68 Barracuda and the trim on the passenger side window doesn't match the trim on the driver's side. I have a spare window with the correct trim, but that window is all scratched. I would like to use the correct trim on the window in the car.

Is it glued on?

Do I pry it off?

Should I heatgun it?

The piece I am talking about is the long silver trim that meets the 1/4 glass.

Thanks!

Check to be sure the trim piece you are referring is not attached (riveted)to any brackets that may be fastened to the bottom edge of the glass. (early b-bodies are done this way, but I am unfamiliar with a-body glass)
If you do not find any mechanical fasteners, you will most likely find a crimp in the trim piece in the vicinity of the bottom edge of the glass.
Use a piece of wood (3/4-1" thick hardwood works good for this) to lay on the glass with the end of said wood piece touching the trim. GENTY tap wood with a hammer starting at the bottom of the glass and work to the top of the glass. Repeat proceedure on the other side of the glass if the trim is not free. Work slow and carefully to avoid damage to glass/trim. For installation, either farm it out to a glass shop or at least get their recommendation to do it yourself. Good luck!