I just did my rear window for my 37. I prefit it because I am painting the truck right now and want to make sure it fit. It is going to be tight and you might need some help and soap and water to get it in. Now I am assuming you have the rear glass frame that hold all this together (no one make this in the aftermarket world, so you have to get one from ebay or one of the guys that sell old used parts) . The screw goes thru from inside the cab and hold the rear molding along with the rear glass in the truck. I put the gasket on the rear window and put in the hold and trimmed it until it fit, then I used a marking pin from the inside and marked where I had to drill the holes in the gasket, then put the screw in from the inside and let it sit so it could form to the hole. Good Luck Jerry

My first prewar and it will not be my last. Done with the 40 for my best friend. Got a 46 (year I was born) to build for me.