I heard about uneven tire wear as well, something small like 1/32" or 2/32" causing the failures.
Going by the old Ford designation (which I don't know if it is accurate or still true), the 6F55 should be able to handle at least 550 N-m or 405 ft-lb of torque. As for 500-600 hp though, would the stock 6F55 and the rest of the car handle that for 100k+ miles as if it came from the factory that way? I've heard the anecdotal claims back in the day, "the 4R70W can handle XXX ft-lb, all that you can throw at it... it just needs this mod and that mod..."
I recall reading the Police Interceptors have ATC's with wet clutches while the retail units have dry clutches? Is that still true for 2013-up models? Which ATC can handle 1700 ft-lb of torque, the one with wet or dry clutches?