1967 Barracuda rear glass

I'm pretty new here and have learned a lot already, but here's a question for ya'.

I just picked up a 1967 Barracuda (last night, actually). It is partially disassembled, but is supposed to be pretty complete. Anyway, the rear glass is not in the car. Once I got home and stuck all the parts inside the car, I decided to "set" the rear glass in the opening while I store it in the shed. When I set the rear edge in the flange and lower the glass down in the opening, the glass is too small for the opening. It has probably a 1/2" space between the edge of the glass and the flange on the sides and top of the rear window opening

So, does 68 or 69 real glass have a slightly different size? I'm kind-of stumped, because the glass is shaped correctly for the window opening, just a little too small, so I think it's for a Barracuda, just not this Barracuda.

Any Ideas???

Did you have the rubber seal in the opening? It will take up that much space.