I have also been thinking about getting a BTS or a John Wood tranny. I have a questions for those that have a BTS I would like to know does Brian put any billet shafts in the trans or are they all stock shafts.
The billet shaft question, I cannot answer. But I do know this:
There was a fellow that hung out a lot over at that "other" forum that had a F-350 with a Cummins in it. He was putting out 800hp or more and doing the 1/4 in under 11.5 sec's @ over 110mph. He was putting that power to the ground through a BTS 4R100 tranny. Everytime he managed to break it, Brian would tear it down, find out what broke, why it broke and put it back together so that same thing wouldn't break again. Eventually, it got to the point where the only thing that was breaking was the custom adapter input shaft that was needed to get the Cummins to work with the Ford tranny.
So unless you plan on putting out more than 800hp, you can sleep easy. I've never been on a dyno, but I'd have to guess I'm doing somewhere around 300hp to 350hp. I haven't been able to break it yet after approx 125,000 miles.