Henry G, you are correct. The T head engine has valves on both sides of the head, each side operated by their own cam. You see those F head engines on Willys vehicles up into the '60s, the famed Hurricane 4 and 6 cylinders. GMCs did run flathead Olds based 6 cylinders (and a few Pontiacs, too) until the 228 came out. It had actually been used earlier, in 1/2 ton panels, on an off and on basis as that model wasn't made in all years. In that model, the engine was referred to as the "Buick type 6 cylinder", as that was it's original heritage. I'll get the exact dates of production. They're listed in the book GMC, the First 100 Years.
