Mr. J, you are correct on two accounts, I looked at a 68 model today and the stamp had the 354U stamp as you said (as well as casting numbers on the right side of the block that are non existant on mine). I'm not so sure that the article I read is accurate. Also sir, you are correct about recommending to talk to an "older, seasoned" guy at the parts counter as I would call them. The younger guys look at at you crossed eyed and say "Duuuuh, whats an Oliver? Never heard of one, duuuuh??" I found one of these guys you mentioned at a Perkins dealer in Houston. A seasoned guy. Thanks J.
One other thing, the set up on that 68 1850 is the same as my 66, exactly. A one belt pulley with the same type 9 bolt balancer.