[screwballl]

welcome to the best source of info around!!!

First, for parts, there are several sources, a few being LMC Truck and Summit and others. Many times you can go to the local auto parts store or order online a Haynes or Chilton manual. The book you're looking for under Haynes says:
Chevrolet & GMC Pick-ups 1967 thru 1987 2WD and 4WD, also includes 1967 thru 1991 suburban, Blazer and Jimmy.

As parts for this could have been swapped out since the late 70s, the last time could have been with a GMC... but it doesn't matter if it is a GMC or Chevy, the parts are the exact same, the only difference is the decals. Especially since the Suburban carried both the Chevy and GMC name, the parts are interchangeable with similar year Chevy pickups, blazers, suburbans. In some cases the Suburbans were a few years behind the trucks, for example, in 1988 Chevy went to the new body style for the pickup trucks but the suburban did not follow this change until 1992.
Have fun with that burb!! the rest of us do!