I agree with 53monster, lower you go, less leg room.
What about tying the springs in the seat back down a bit. If you pull the seat back out, you can see this is done along the top, with little chains. (at least it is on my '50) I just reupholstered the seat in my '50, and pulled the springs down for more room. Not so much for more leg room, but so I didn't wear the paint off the steering wheel. The result is the same though, you end up sitting a little farther from the firewall. You might wanna give that a try, as it sure doesn't cost much, or take long.
