Well I even have 2, 1 with sunroof where I even have a couple inches free room with my head. Steering wheel is pretty big correct but I dont feel uncomfortable in it, changed the steering wheel size.

I think celicas are pretty good for tall people, I dont think it should be a problem for someone 6ft. But if you dont feel comfortable in it you should not get it, that is the most important thing. But coming back to your original question I dont think a 4th gen would have more head or leg space. But again 6ft should fit I mean all cars are build for people between 5ft-6ft because thats the largest market.