The tallest F1 driver of all time was Justin Wilson of the UK, he stood at 6'4" (1.93m)
Blimey! How the heck did he fold up into the car!
Having this last weekend attempted to sit in Jonathon Palmers ageing Tyrell F1 car, I can confirm that someone (me) of at least 6' 3.5" can fit in it. The only problem is that my arse is significantly bigger than his was, so I couldn't squeeze down into the actual seat as it was moulded to his physique (which was not as "ergonomic" as mine is).
Comfort, on the other hand, is not guaranteed as the cockpit in those things clings to the shoulders when you are that tall.
But they can be designed to be more "tall-friendly" - lookit here:http://www.youtube.com/v/VGrCpS1BR2c&fs=1
That person driving just happens to be 6' 3.5" by an amazing coincidence.