If you have cracked, broken or missing 1/4 windows, you may want to get in on this.
Ken Hines in Florida is having a sale (to Dec6) on ebay or thru his site on repro windows. I have not seen them but have heard they are not bad. Not the same as GM but close. These ones are clear and are now just US $99 plus shipping.
See his website at
www.kahines.com