Here's a pic of the stop that's attached to the bottom of the window sash, and a pic of the door where the bottom stop bracket is welded.
Man, there's gotta be an easier way to go about this... i can't be the only person who's ever had to change window sweeps lol...
all the ones Ive done, (Chevy, Eldorado, skylark) have the one that was explained here.. adjustable L bracket bolted to the inner door with some fuzz on it. window rolls down and bump stops right on it. if yours is tacked or riveted in, Ive never seen one myself but you should be able to just simply drill the weld or rivet out. remove bracket, and window will drop. and when you reinstall, just roll the window down to where it looks like it should stop, mark the spot, drill & slap a bolt in there. easy.
Old thread but maybe my advice can help as I just changed my window fuzzies. 1969 Skylark: rear windows had adjustable window stop. I used a 7/16" socket to loosen the bolt and the L-bracket was removed allowing the windows to be lowered that extra 1/4" to get at the screws in the window felt. The front windows did not have the same system. The channels that the rollers move up and down have a rubber or plastic stop in the channel about 1 1/2" long and the exact same width as the channel (about 1 1/4"). I could get the stop to slide up and down but couldn't get it out. probably was removable at one time but the hardened rubber is more like plastic now and not flexible. One side of the car didn't have the stops so that window went down about an inch lower than the other. I figured it can't be that bad so I finally wedged those stupid spacers out of there and left them out. The only danger I can imagine is that you can lower the window too much and possibly pinch the rubber on the way back up with the window. The window seems to rattle a little bit if rolled all the way down. Good Luck.