Earl, Tis a good ? you put forth. I own quite a bit of pre-unleaded fuel crap. In all my instances when it's time to pull head and get to the valves...I have always had to put hardened exhaust seats in (intake are cooled by the fuel charge and don't pass on in the same way). In all the while I've been lurking on cruiser boards this ? hasn't come up or I haven't been paying close enough attention. I would guess based on my ex that if your needing the valves reworked....put new hardened seats in the exhaust and new ex valves in to. Let your machinist pass judgement on the intakes. My 02.