First thing I did was measure the thickness of the window lip which is 3/16". Then measured the thickness of the
fiberglass at the window opening, mine was 3/16". However the rubber weatherstrip was not available in those measurements. I found part # AS1456 to have one groove 3/16, and other groove 1/4", same as original, so that is what I bought. I think length of original is 7 feet ( measure to be sure) so I cut the new weatherstrip to be 2" longer. You'll need two or three people here, put weatherstrip in window opening, tight to
fiberglass opening, with the 1/4" groove on the
fiberglass. This is like wrestling a snake and takes extra hands to hold it tight. Groove for lock strip should be on inside of trailer. Once weatherstrip is tight in opening, cut off the extra so ends butt tight. Joint should be halfway up one side. With helpers holding weatherstrip in, lube inside with dish soap. Using a hook type tool (auto part store should have one, my NAPA did) Work window into weatherstrip from inside. Once in, lube and install the lock strip with the Lisle tool. Be careful with the hook tool, don't use one with a sharp point. There may be two 1/8" drilled holes at top of window frame on outside that the rubber doesn't cover. Use some type of caulk to seal them. As for the window channel, I have no advice as I found a couple new old stock original
windows. If you replace the window channel be sure to open up where the weep holes are. The openings for the side windows apparently were not cut out very accurately, so sometimes the windows don't fit good. I had a lot of spare parts but
sold them all, deleted most of my photos, and burned most of the files I had about Uhauls after we
sold ours. The facebook
Uhaul group has a lot of good info.