There is a flash that the dealer can do to make the "tow/haul" button on the '05 work like the "od on/off" button like the other years, BUT...I've heard that anytime you load a new program onto the truck from a programmer, it erases that flash. I purchased the BD Overdrive Lockout box and it works good. I think the price is around $200, should be able to find it from one of the sponsors here.
Jared