Just ordered a set of smooth back Rally seats and rear seat cover by Procar (Scat). The regular Rally's are what you see advertised everywhere but I found the smooth backs on their site and liked them better. Jeg's will do the whole package of both seats in black vinyl, seat adapters for '67-'69 Camaro, and Rally rear seat cover for $862 shipped. They're available in leather and other colors of vinyl, velour, or combination as well. There are a few other Procar seats that are less expensive and look good but the Rally's just look right to me in my '69.

Procar site:
http://www.procarbyscat.com/

Smooth back Rally:
http://www.procarbyscat.com/images/products/Rally_51S.jpg

Regular Rally
http://www.procarbyscat.com/images/products/Rally_51.jpg

The smooth back seat looks nicer IMO...