Are you guys talking about keeping the t/c from locking up? IF so why? That would not be anywhere close to an accurate reading.
Secondly, on a powerstroke, you need to run the dyno in OD, if you don't you will not get into the upper fueling tables and load up the truck like Luke said.
If you just put it on the dyno and then hammer it through all the gears you won't get an accurate reading either.
The operator, should put the truck on the dyno, get it into OD find the downshift point and start the run above that so there is no shift spike or anything.