Actually you can get aftermarket seats to sit you lower than stock IF you don't use a sliding bracket and mount them directly to the floor. I rode in one s14 with Sparco EVOs bolted directly to the floor, even with my helmet on I had a good 3 inches of head room with the sunroof. The draw back there is that you don't have any adjustibility so you better pick a seating position that works for track and street or make a compromise
. Short of that you wold need to find a s14 without a sun roof.