Original glass, or brand new? You install or they? Who makes the patterns? Who supplies the new rubber and the fuzzies? Just lay down the back window, right? If you expect the curved rear window to be cut, add about $500.
All new glass (including windshield) could be anywhere from $500 to $1500 depending on where you are, who does it, whether or not you also need new rubber and fuzzies, etc. etc. I had all new glass cut for a '50 Ford for a couple hundred a few years ago. I had new SIDE GLASS for my '53 Chevy done last year for less than $400. You can't cut the rear window, but everything else on your car is just flat glass so it's not that big a deal to just cut it or cut brand new glass to the new size and shape.
If you do some of the work,it is less $$.You make the pattern,let the glass man cut it out,u install..maybe 30.00 a winshield(u need 2),i am talking Compton, CA $$$.