I'd say 6'4" and under you'd fit, but it's pretty uncomfortable with the roof down. Not a car to drive with the roof down anyway, very noisy, poor visibility, and ... well, kind of pointless, really. The fun is in the openness. Transforms the whole experience, and connects you with the surroundings more in the way that cycling does.
Smaller steering wheel will also help (this hideous wooden one was quickly replaced with an original MOMO which is better fitwise)