This guy on ebay has both left and right NOS windows
http://cgi.ebay.com/ebaymotors/NOS-87-88-Ford-Thunderbird-LH-rear-quarter-window-glass_W0QQcmdZViewItemQQhashZitem2eaad463e6QQitemZ200434541542QQptZMotorsQ5fCarQ5fTruckQ5fPartsQ5fAccessories
If someone could pick that up for 30 bucks, thats a hell of a deal.