In the past I have bought these for 80's Greco restorations and they were drop in replacements. I believe they are made by Gotoh?
http://www.stewmac.com/shop/Bridges,_tailpieces/Electric_guitar,_Tune-o-matic_bridges/ABR-1_Tune-o-matic_Bridges_and_Parts/ABR-1_Tune-o-matic_Bridge.html