jim will correct me if i'm wrong here, but his car is (was B) ) a 68. and as far as i know, the only unmodified peice of glass on his car is the rear oval glass.
josh, anything is possible and you should be able to graft an oval rag roof onto your 59 while chopping the roof at the same time. however, you're going to have to modify the glass. a 59 windshield is slightly larger than an oval windshield, but imo, if you're going to chop the roof, you'll want to get a modified peice of glass for the windshield. you'll also need to modify or get custom door and rear glass.