D-2 Chev 6 & S-Pickup

Don't get me wrong, the Stovebolt 6's were good engines, ALl of the American inline 6's were good. What kept the Chevy from being great was the primitive oiling system. They could have even stuck with the babbit if they had drilled the crank for the rod ends.
I can't remember where I read it, but Japan's automotive reputation up to the middle 60's was crap, they just hadn't figuared out how to make good rings. It was Honda's Accillies Heel. Once they got it figuared out, they really took off, and surpassed the US in later decades.
The GMC V6's were an odd duck in a way, 1st they were only used in trucks, 2nd they put the plugs on the inside (in the vee) of the head, 3rd they were made in both gas and diesel, but the diesel didn't have a good rep, and 4th like their distant cousin's (Detroit) they were "modular" in that they were made in 6, 8 and 12 cyl veriants. The 478 being the largest displacement V 6. Not many 702's were made, and I can't imagine feeding one! They were a monoblock V12 but based off the 351 V-6, the block,crank and cam were unique to that engine, while the pistons, heads and manifold were like the V6.

Interesting background on the 305 V6!

on the GMC page they go gaga for the military GMC 302 inline 6 motors, they put split Fenton headers and 5 or 6 carb intakes on them