I am trying this out on my '66 since it will be a while before I can do a proper replacement. So far it is working really well so I thought I would pass it along in case no one has thought of it before. The felt is completely gone in my window channels so I picked up some thin felt sheets at wally world. I used a paper cutter to cut them into 1.5" strips. I cleaned the channels with a small wire brush. I applied 3M weatherstrip adhesive into the channel and spread it with an old flux brush. Then pushed the felt into the channel using a small putty knife with the excess even on both sides of the channel. Then roll up the window to seat the felt evenly. I did the top first, then one side, and then the other. With the glass up, trim off the extra material when the adhesive is dry. I have only done the exposed channels so far and it is working great. The felt cost 29 cents each, $7 for the adhesive and it took about 15 minutes to do.
I think the horizontal anti-rattlers are going to be the most challenging.
john

 

I read where someone did the same thing with the fuzzy side of Velcro.
Hope it works out