As Tom said above, unleaded gas should be fine. Many people, myself included, use Marvel Mystery Oil, mixed 4oz. to 10 gal. gas. Just dump it in the tank. It's a top cylinder lubricant and cleaner, so they say. I was told it would help in combating vapor lock. The only time I experienced vapor lock was when I rebuilt a fuel pump and didn't put an important seal in it because it wasn't in the pump when I took it apart. Eventually figured out what that "extra" seal was for. So, does it work? MY experience would be yes.

It also is supposed to keep your valves and piston tops carbon free. After logging many miles on a flathead, 6cyl. Mopar I decided to rebuild the engine and the top end was absent any carbon deposits. Did MMO cause a carbon free top end? I can't say for sure but after using it on that engine for years the top end looked like MMO said it should, thats all I know.