[GMCNUT]

So GMC was married to GM sister division Pontiac in the 40's and 50's and shared Pontiac's design team for engines. GMC used Pontiac car V8's from 55-57 before Pontiac designed GMC its own variation of the 1958 Pontiac 370 V8 which was a smaller bore 336 V8. In 1959 when Pontiac went to the famous 389 V8, they gave GMC another version of the 336 V8 which had a shorter stroke and was based on the 389 V8's bottom end. This version of the 336 was slightly faster in terms of horsepower over the previous years' 336. During these years, Pontiac engineers developed the V6 as a means of giving GMC its own engine that would give the trucks a distinction from Chevrolet and give them the powerful low end torque they are known today for. You can see the Pontiac engineering influence in the power steering pump and fuel pump designs and the way the V6 intake still sits up on top, separated from the push rod valley vs a Chevrolet fully enclosed design. Everything about the GMC V6 design and appearance screams Pontiac when you compare to the early V8's Pontiac shared with GMC. The V6's are the last stand from Pontiac before GM fully aligned GMC with Chevrolet by say 1966 or so and started offering Chevrolet engines in GMC's. By 1969, the V6 was over with, and the Chevrolet V8 won out over the V6 for cost and efficiency reasons and maybe other things like fuel economy. Not sure if this answers your question any but I believe this to be correct unless Pete, Ed or some of the more knowlegeable and experienced V6 users have anything to add that might shed any more light on the subject of who came up with the V6 design