I believe all the trannies below can be built to be very stout. The 4R and 700R4 would be the strongest of the group though.
AODE
Pros, Bolts up to Ford Engines, Shifting is tuneable through Computer control.
Cons, Tall Gear set, Cost extra for computer controller, early versions should be upgraded for max reliability, ( AODE was only available up to 96)
AODE 4R70W ( later version of AODE with wide ratio gears)
Pros, Bolts up to Ford Engines, Shifting is tuneable through Computer control.
Lower gearset than earlier AOD or AODE and C4. 98 and up versions have good reliability upgrades built in.
Cons, Cost extra for computer controller, early versions should be upgraded for max reliability
AOD
Pros, No computer controller required. Bolts up to ford engine. about 3/4 of an inch shorter than AODE/4R70W
Cons Tall gears ( can be upgraded to wide ratio gear set for more $), Shift profile is set by trans builder, not easily changed.
700r4
Pros Lowest gear set of all the trannies above. No computer controller required.
Cons Needs adapter to bolt up to Ford Engine. Requires more custom work to make it all work with the Ford setup than the Ford trannies above.
C4,
Pros, Cheap to install
Cons No overdrive, tall first gear, shift profile must be set by builder
Tom