[Stocker]

Totally depends on your engine. If it's been rebuilt within the past several years, it probably has hardened valve seats, so lead / lead substitutes aren't needed. I believe one of the few (maybe the only) benefits of leaded gas was to lubricate the valve seats to reduce wear. As to octane, it depends on what your engine needs. Mine is happy with 87 octane regular, doesn't matter what brand.