The reason your lower back hurts makes a big difference in choosing the most effective way to deal with it. I have 2 herniated discs as a result of a lifting injury. A friend who is a Doctor has a back injury as a result of a fall he suffered in martial arts. And our seemingly similar back problems have very opposite symptoms. I can sit for long periods without discomfort; but standing for long periods without moving often makes my back hurt. My Doctor friend cannot sit even for a short time; but he stands all day long without discomfort. And the car seats which work best for my doctor friend do not work well for me.
Most power seats have a tilt adjustment as well as a height adjustment for the base. Some people with back issues cannot drive a car unless it has a power seat; fot this reason. My experience with the best vehicles for tall people has been that Subaru Legacys fit tall people better than most other cars, and also have one of the most comfortable seats.
The 2002-2007 Suzuki Aerios were designed with an unusually high seat base. I don't know whether one would have enough head room for you; but it might be worthwhile to try sitting in one.
Over the years, I have found that both my awareness and use of my posture, along with my overall health; have more of an effect on the amount of back pain that I expereince in a given seat than almost anything else. By working on optimizing my health (which always has been pretty good; but which I discovered can still make a big difference in my overall pain level, if I am careful to eat the best possible diet, get plenty of exercise, and sleep in a FIRM bed). Beds that are too soft do more to ruin my day than the seats I use. An air bed with adjustable firmess control can be a godsend.
If you're open to seeing how much diet can affect this; check out www.drfuhrman.com
One of the most valuable things i ever did for my back and posture was to take 1 1/2 years of lessons in the Alexander Technique of body and movement awareness. You can find local practitioners of this widely used technique (by athletes and actors) by googling it and looking in a telephone directory (both white and yellow pages).
Some types of kidney problems cause lower back pain. Even if you don't have kidney problems; drinking 6 to 8 glasses of pure water daily, and avoiding soft drinks can do a surprising amount to reduce lower back pain.