I myself will be doing this install in the future and this is what I've learned so far from doing the research.
6.0 Cooler bolts directly into where the original cooler is.
If your truck is a 99-2000 you will need about 4-6ft of 1/2 in transmission hose(the 6.0 cooler has 1/2in inlet and outlet fittings rather than the 3/8in that your original has).
If your truck is a 2001-2003 you should only need 2-3ft of 1/2in hose because you will have hard lines that pass into the bottom of your radiator first and then go up to the air/trans oil cooler, so basically there is less rubber hose in this case. This is how my truck is set up.
1/2in transmission hose will be hard to find at your standard auto parts supplier, napa can get it but I think they only offer it in a 25ft roll. Heavy truck service locations should have it. Don't let anyone sell you 1/2in heater hose because it's not rated up to temp or pressure. I believed 1/2in fuel line is up to the rating but I haven't confirmed it yet.
As far is fittings, you will need to adapt from the 3/8in line up to the 1/2in line. This is easiest done with brass barb type fittings and hose clamps. Some people use one female threaded barb and one male threaded barb, put them together then you have a union that will work.
Although, check out this website
BRASS FITTINGS Brass Pipe Fittings Hose Barbs Stainless Steel Fittings Hydraulic Adapters Hydraulic Fittings Grease Zerks Hose Clamps you'll find everything you need for fittings and they are pretty cheap.
I'll be using this fitting which in my opinion will be the easiest, it's a straight union that goes from 3/8in up to 1/2in, and dirt cheap
Hose Barbs: Hose Mender
Like I said I haven't done this yet but it's on my list of things to do