Explanation:
1. Weren't as many GMC's made as Chevy's so they had more leisure time on that production line.
2. GMC's were made heavier, stronger more durable than the Chevy
so more effort went in to making it that way.
3. GMC's cost more that a Chevy so they didn't have to skimp
on the cost of a bolt head. It's been the subject of discussion
many times of how Chevrolet Motor Division was full of penny pinchers.
dg
