If you are talking about the windlace that "slides" in the track around the door, get a dictionary of curse words because you are going to need more than you have ever used. I just finished both doors on my 49 last month. I will be having my hernia repaired soon as a result. Not really. My tips would be as follows:
I used liquid dishwashing soap as a lubricant along with Armorall (sp?) Get out your shop manual as it is some help. The repop rubber is not notched as described in the manual but by holding it in place I kind of guestimated where to notch it, which I did with a razor knife. I think that the profile of the part of the windlace that actually slides in the track is a little thicker than original and on one door I took a rotating stone in a Craftsman (dremel type) tool and thinned off that part of the windlace. Be sure the track is free of crimps before you start. I helper is almost necessary to keep the rubber feeding into the track as you pull your guts out trying to get it in. As you pull the rubber is thinned out by stretching and slowly it will feed in. When you get frustrated stop and come back later. Lots of lubricant to the track and the rubber. I had some silicone lubricant but the can said it had acetone in it and I was afraid it would damage the rubber. I got mine from Jim Carter as he was the only one that I could find advertising the greyish brown color original to my 49. Later, I think they were black. I had some of the original from when I disassembled my truck and that is why I think the profile is slightly different on the repop and on reason it is so hard to intall. If it had been that difficult and time comsuming at the factory the trucks would have cost 10 grand in 1949
