We have two KC area EP RX7's running 4spd Jericos and they have been very reliable. They both used Y2K boxes with drilled shafts and lightened gears. One of the guys sourced his from a NASCAR team that was using it for roadrace qualifying. As others have mentioned - you use all four gears on the track.

To fit these in an first gen RX7 they did have to hack up the tunnel in the car allot. It is a big box.

I looked at the G Force transmission for my RX7 but I wasn't all that impressed with the gear ratios. Also, unless G Force corrects this, the 5th gear in a stock T5 is in single shear. I'm not sure It would be all that strong.

I'm going to use a Miata gear set in my car.