Modern A-body glass?
I have researched this modification, camaro and mustang guys have been doing this for some time. instead of using custom glass, they build out the frame a bit to accommodate the difference.
although eventually some one did make a drop in kit (specially sized glass) but i guess you can do that when there are thousands of mustang/camaro guys to buy it.
when googling try "flush mount glass _______________"
http://www.camaros.net/forums/showthread.php?p=1478676