My 69 GTO was almost identical to my brothers 69 Chevelle SS, as far as radiator, fan. under hood, body etc. But the 396 had main bearing clearances greater than the clearances in my 400. His ran cool mine ran hot. I don't know if I go for that close clearances equal hot oil or not but I was always fighting high temps and he just put the foot down and didn't worry about it. We seem to have more problems than the Chev guys, and the rads, fans, hoses, heater cores and what have you seem to be of the same breed but we always have that temp problem???