I am assuming that you are talking about a hard tonneaus cover? If so, I had one put on my '72 chevy from CheckMate (
http://www.checkerpro.com) It is a flush mount (has a small lip that sits on top of the bed), fits fine. When you order, they have you measure your bed just to make sure the cover will fit. They also make custom sizes (i think). I used to have pics of the truck posted here before the DB crash. Will try to do it again if that option is still available.