Slider to Solid Back Glass?

[wixthedog]

Good morning everyone, pull up a chair and let's have a chat.

My 76 came with a (factory?) sliding rear window which I hate. Many moons ago a thief gained entry to my pickup by one and took my massive CD collection binder that we all had in the 90's. Needless to say, I was distraught then still am today. Oh, and solid glass looks better.

I found a steal of a deal on a takeout OEM solid back glass but I will need a new gasket. I started looking at them on various sites (LMC, Precision, Amazon, etc) and they all say the same thing:

"Rear Window Rubber does not fit trucks with factory sliding window."

So, does this mean that the gasket is not fit to replace a gasket on a factory sliding window or does it mean that my cab opening is a different size?

Any thoughts or experience here? Thanks in advance, you guys are rock stars.