To match a waggy width you'll have to cut both sides down, but that's another subject....

I've already popped out a window to see what I'm dealing with. It looks like it shouldn't be too hard. I think I'm gonna use the front of a truck bed to build the lower wall of the new cab and fab a window frame to accept a Ford Ranger sliding rear window. I like the Fords cause they are the tallest mini truck window i've seen. By using a after market slider window I can have custom glass made if I have to narrow the frame any. I don't know yet though, I'll see when I get there.