They run fine on 87 unleaded Andy. The lack of lead for lubrication of valves isn't an issue, and octane "is what it is." The only differences are you need to tune them to run richer than you did in 1970, and if you leave them alone for six months, the fuel in the float will condense causing water, which will turn some of the carburetor components into powdery white stuff, or downright rust.
The other day for the first time, I broke down and went and bought some alcohol free 94 octane at one of the pumps here in town. Big difference in performance that I didn't even realize I was missing until I tried it. I bet it will turn into regular gooey shellac in the carb now, instead of metal corrosion after six months. :laugh: