You can use any window of your choice. My 64 C20 happens to have a 71 Ford slider. We're pulling it to put in a one piece glass; no slider. It looks like the sheet metal was just cut to fit, and the window installed with a new seal (looks a bit flimsy to me but it's been in there a long time). It'll be interesting to see what they actually did when we pull the old window. The new one will be put in correctly regardless. I also installed one piece power side windows. What a project that was!
