man there are some 5R110 haters over on the NATION, they seem to be pro 4r100, its interesting. and I hope that I dont have this kinda problem.
It isn't the tranny that is the issue it is the computer that controls it. There is one major difference with the trucks you just talked about and what you are planning on doing with your truck, HIGH AND LOW RANGE. They use different shifting tables and different reasons for shifting. In super simple terms, in high range it can be programmed to shift on rpms for racing, you cannot use rpms in low range. You also can't get the TC to lock up right in low range. So then you will be trying the lockup button idea and that will limp the tranny. Then you will try to put the wire behind the glove box to not let the truck know that it is in low range. Then it will shift great for about 200 ft, then the truck will figure out through the tires are spinning to slow for high range and then limp the tranny.
I have had 3 different transmissions in my truck and somewhere in the neighborhood of 5 different convertors in the last two years. I have had 3 different vendors trying to get the programming right. Could never get the tranny shifting right.
So if you want to pull, don't use a 5R. If you want to drag race the 5R is a great transmission.