Depending upon how old the valves and seats are -- and what type they are -- you may or may not.
If they are old, they are probably the original type. If it ran leaded for most of that time, you should be fine with unleaded. The lead from the gas has permeated the seats.
If they're new(ish) and the original type, then yes. Put a leaded additive in the tank.
If they're the new hardened type, then you will be fine with unleaded.
