I would almost guarantee that custom gears would cost more than a Mitchell. Why re-invent the wheel. Since I put a Mitchell on my truck with high speed rear, I can easily do 45 to 50 on the highway.
Frank
I can do 50 with high speed gearing alone.
I guess when I mentioned the speeds I achieved, I implied that my engine was running at a speed that would keep it together. With standard engine components for the A, your engine must be running over 3000 rpm. Go for it...