This might be apples to oranges but my 56 gmc with 248 all stock seems to go 65 without any trouble, I have had it over 80(back in my youth, late 70's). Now I'll be the first to admit that was a stupid thing to do, but it brings up a question that I don't recall seeing before,(but I'm sure it has been asked), what is the red line number on these old sixes?
