I forget if it was SAE20 or 20wt, but I think they are the same grade...but, does anyone in the USA still produce 10 or 20 weight non-synthetic motor oils?
Even though it doesn't have an SAE rating, Chevron Delo 400 is available in straight 20. If it's as good as their 30, it'll be pretty good oil. Chevron also makes the Texaco Ursa 20W-20, I've never used (nor seen) that oil, personally.