I'm 6'-1" tall, with a 36" inseam, and about a 76" wingspan. So, long legs and arms, with a comparatively 'short' torso. I always slide the driver's seat all the way back, in any vehicle, so that my arms and legs are as straight as possible. Headroom is rarely an issue, except I do have to make sure to bend at the waist and knees to not bang my head while entering or exiting modern cars and trucks. I have a buddy who, at 6'-3" sits in a car the opposite manner that I do, with his legs crouched, and knees bent behind the steering wheel, like a preying mantis.
I believe the problem you are experiencing is not so much with the height of Tesla Motors' cars, so much as it is the height of the floor. A traditional motor vehicle has only a bit of carpet, padding, glue and sheet metal underfoot. A Tesla has a 4" thick aluminum box under the entire passenger compartment. That can make a significant difference in perceived interior comfort.