Yea I don't recall seeing 10w-30. 10w-30 was just too light! I don't recall Ford recommending 20 but I know GM did.Interesting reference. My recollection from back then was that 10w40 and SAE 30 were the main grades. One could find SAE 40 and 20 but anything else was not too common. This may depend on the region too.
When multigrade oils became the standard that pretty much eliminated the summer/winter grade regimen. Even back then, habits were hard to change.