There are many old GMC truck experts/owners at oldMCtrucks.com discussion board.
All questions on that discussion board do get answered, usually expertly and politely.
Some members there are also members here.
Some GMC owners post the same question at both forums, eventually migrating to the forum that seems to be more helpful for their trucks.
When I had both types of GM trucks, I'd ask my GMC questions over there and my Chevrolet truck questions here.
