I checked with Craftec and the only tonneau cover they offer for your 1972 Chevy El Camino is the part # 252198 that you referenced. This is a heavier duty tonneau that would work well though. view full answer...
The Craftec Tonneau Cover part # 252198 that you referenced does fit 1968 through 1972 Chevy El Caminos. This would be a confirmed fit for your 1968 El Camino. view full answer...
The Draw Tite hitch # 75082 does not fit any Chevy models actually. It fits the following:
1994 - 2010 Mazda B Series Pickup
1983 - 2012 Ford Ranger
1986 - 1989 Ford Ranger excluding GT view full answer...