If the frame is indeed nice and you don't mind doing some body work and have a decent engine to put in it, it could very well be a nice sleeper. I have been complimented more on my '78 LeMans sedan than I ever was with the '78 2 door Cutlass I had, so if its something you would like to work on, I'd say to go for it. I originally bought my sedan just as a car to pass some time with, but after having the Cutlass and an '85 Grand Prix, I quickly discovered the sedans have more long term body integrity over the coupes IMHO, as the doors are lighter they don't wear the hinges and sag, and the door windows are fully framed and stay sealed up much better over time. I've never been worried about fitting in with the hot rodder crowd having to own a coupe, thus I favor the G body sedans and wagons. On the plain jane G body Malibus and such, if you put a set of classic Cragars on it, people will have to take that second look to even realize it's a sedan.
-UT-