Jon,
I have been running a 7.25" Tilton twin disc (sintered metal) for three years and found it to be totally trouble free and actually very driveable (my car still has a license plate). The engagement point is precise but just takes a little getting used to. It's the only clutch I've ever had in the z that has not failed in some way. Mine's mounted on a Tilton flywheel but the flexplate option is better for a track car I believe.
One bonus, you can sometimes find smoking deals on the triple disc version since the nascar guys use them as well.