When my then-new '64 Custom/427 was a couple of months old, I took off from a light at about 1-3rd throttle, granny-shifted into 2nd and discovered that there was no connection between the engine and the rear-end. When I got the trans---a T-10---out, I discovered the output shaft had twisted off. I was working at T&C Livonia and knew the Executive Engineer, Bruno Zava. I asked him nicely, and he had a big in-'n'-out Toploader delivered to the local dealer for me. (Toploaders were not yet in the parts chain.) I had to get a new clutch disc and driveshaft yoke to make it all fit, but that cured the trans troubles, likely forever. And the Hurst shifter I'd installed practically right away after taking delivery of the car had to have some change parts as well.
The T-10 simply isn't strong enough to take the torque a performance FE will put out.
KS