Welcome,
If you plan to work the truck you will want the two speed.
With a name like "dt466man" I expected you to want to swap an IH 6 cylinder diesel in a truck.
If you do plan to do that then get the truck with the best body, and the most common rear axle with an available faster ratio you can swap.
Many people swap diesels in trucks and don't plan out the rest of the drive train and gear ratios first, don't be one of those. They are left with an extremely slow and almost useless truck.
http://www.drivetraindirect.com/t_gear_calculator.htm Should help if you start to swap things.
Grigg
