it seems that you are displeased with the "jerk" that the truck makes when it is shifting a low speeds, this jerk is something that I would assume to be normal, especialy in a truck that is designed to haul things.
a firm shift = a pronounced "jerk" when shifting from gear to gear
a soft shinf = a silky smooth shift, that you only know it shifted because you saw/heard the RPM's drop.
a firm shift is more effecient, and usualy better for the transmision, as there is less slipping going on.
in a small car you can afford to have a soft shift, as the tranny isnt working all that hard to move the car around, so the heat buildup is less.
now I have read the origonal post again...
and thought about it... and maybe you are talking about the fact that the tranny shifts too soon? I.E. you floor it and it shifts before red-line.
if the latter is the case, then I am sure there is something out there.
Well, I have an '03, and I feel the shifts are too soft, especially the 2-3 shift. I found a kit from Transgo that is supposed to firm up the shifts some. I will hopefully install it this weekend, if you want feedback on this kit.