About 6 or 7 on a '53 SC. My left leg had to be long enough to push the foot clutch pedal while sitting on the edge of the seat.
Actually started driving at 5 or 6 on a '23 1 ton Model T truck. Went til I couldn't hold the go pedal down any more, rest foot and go again. I wasn't allowed to use the direct drive (high) lever.