The only issue with unleaded versues leaded fuel is detonation. If you can obtain unleaded fuel with sufficient octane to keep the engilne out of detonation, then don't worry about the valve seats.

Even vintage Amercian engines with non-hardened integral valve seats in the cast iron heads do not have a valve recession problem unless they are run very hard such as racing or truck duty, and then the engines only have to be run with leaded fuel early in their life as this will build up a thin lead oxide film on the seats, which will mitigate seat recession for the life of the engine.

Further, if you engine has an aluminum head, it has OEM installed hard valve seats already.

Duke