I know that I'm new to these cars and all but before buying one I just have to ask. Didn't these cars originally run on "regular" gas, not unleaded? If so what is everyone doing? Putting in a fuel additive?

You could/should use a lead additive if you do noy have hardened valves & valve seats. Otherwise have hardened

valves & seats installed.

- Jeff

When pulling a head off the block, is there anyway to tell if the seats have been replaced with hardened seats?

Oh yes,

None hardened seats are made of brass.

Yellowish in colour.

Hardened seats are steel, steel in colour!