J, at 6'4", you're going to have a hard time passing the 'broom-stick test' regardless of the bar. The Deuce does sit the farthest back, but that also flattens the imaginary line from windshield-header-to-rollbar. Start with a foamectomy, and see where you end up. IIRC, the '95M seats are shorter (closer to floor) than regular NA seats.
PS
Here's the AX calendar - http://www.dfwmiata.com/content/3-autocross-calendar
PPS
Seat time, seat time, seat time.