If it has not already been mentioned, I would look into buying a torque converter than has been opened and had all of the veins welded. There are some other high failure items in the torque converter that can be strengthened as well. That said, my dad had 3 transmissions that were completely wiped out due to the torque converter coming apart and sending steel shavings through an otherwise good transmission.
1990 ¾ ton 4x4 Chevy Suburban
-Cummins Diesel - 12 valve - factory rebuilt
-6 speed bullet proof manual transmission - NV5600
-Gear Vendors Overdrive
-Upgraded Holset HX-35 turbo
-NP205 iron transfer case
-3.73 gears
1982 ½ ton Chevy Suburban
-6.2L diesel - high nickle crack free 1982 block
-Stans headers
-Ported heads
-Timing gear
-4 speed automatic
-3.08 gears
-30 mpg on freeway