HAWK: I heartily agree with CERBURISM, if you can possibly find a local transmission rebuilder & discuss you needs. I got lucky here in Racine, WI with GT Transmissions. I too was tempted to buy ATS, Goerend, et al. I mentioned this to GT & they were OK with installing anything I wished. The soft sell got to me. We talked. I got convinced they could build anything to do the job I needed.
By the way, they had a split input gear from one of their "good customers" for me to evaluate right on the bench with her parts & pieces. OEM input shaft is pressed into a triangular splined gear. This spline geometry baffles me, in that the triangular shape forces the "hole" in the gear to "open up" under stress. I gladly agreed with the $729 billet input shaft.
Glad I'm a shadetree mechanic & understood most of their lingo. Bottom line... they quoted an aftermarket torque conv. rated @ 1200+ lb-ft torque with 500 RPM reduced stall speed to make best use of diesel power, performance 3rd gear disc pack, Kevlar 2nd gear shift band, aftermarket pressure regulator, billet input shaft, slightly modified shift kit, etc. , etc. and 3 yrs. or 100K miles 100% parts & labor warranty. I was cautiously stoked. $4300 complete, done in 2 days. We left for Orlando 2 days later. Getting a Goerend or similar transmission shipped & installed would have been another $2000 in my estimation.
I feel very fortunate to have found someone trustworthy to build it locally. They were just fine taking a few calls from the road with some general questions I had. I pushed it @ Banks Pwr. Lvl 6 all the way to Orlando & back, looking for any sign of trans slip, shifting bumps, etc... nada. I love my truck.