I don't know exactly what the throw-out bearing looks like on the GT. I presume it to be a hydraulic kind like McLeod type. My experience is they are great for street rods and hot rods. When I used one in my small block 68 dart we were twisting it to 9,200rpm at the launch and it would leak after a few runs.
Finding out heat cooks the fluid just like it does in brake calipers. Once that happent the high temp Viton seals get real soft and the pressure leaks past the o-ring. Damage is done but if you let the seal cool then you can get by for a short time.
To prevent high heat to the throw-out bearing, don't sit with the clutch in longer than necessary. Pop it in neutral and let the clutch out.
Dave, did you do the Woodward crawl recently?
I know Rich will do a wonderful job taking care of your rocketship but maybeask him if they can bleed and replace all the clutch fluid, the air will make a clutch shutter as the piston in the bearing moves in and out compressing the trapped air in the lines.
Of course if it's not the hydraulic type then I am all wet:ack