For a T1 CSU/DSU:

Its wires 1 and 4 together then 2 and 5 together

For a 56K CSU/DSU:

Its 1 and 7 together then 2 and 8 together.

Maybe they have one for the 56K but are not advertizing it. I would contact them directly and check on that. With an order of 900 I would assume they would go ahead and make some up. As it would not take a whole new dye but just a change in the pins.