I think you are looking at a med duty truck trans for that kind of set up.
Eaton Fuller 5406b and friends.....
http://www.vibratesoftware.com/html_....htm#FSB-5406B
These are going to be LARGE case units with twin counter shafts, and they aren't even double OD. Not very suitable for swapping into many light truck applications, but anything can be had with money.