I am 6'4" almost 6'5"... at Cedar Point.. it's ridiculous, so I have developed some tips that may or may not help you or other people reading.
When riding, go for the front seat on a car, it typically has A LOT more leg room than the car behind it.
Get in the car first- you'll need the few extra seconds and room to get situated.
Try the test seats- If you can't fit, it's better to know before you wait an hour for the ride.
Jeff