Here is a link for some US Gear info. Looks like the company has been bought out and the unit is being redesigned.
DualRange Overdrive
Maybe what you should have said is you have a "CUCV truck with a TH-400 and NP205 case." This was you would not have to explain why you have a M1008 with a 205 case since they obviously never made them.
I am not familiar with this unit but have a Gear Vendors OD unit on my M1031 with the TH-400 and NP205 case without the PTO on it and it has a pick up bed on it (not that any of that matters other than the TH-400 with 205 case for adapter purposes) and a 91 Suburban grill and home made front bumper with 18K Warn winch. The way we did mine was as follows: The GV was in an old Dodge running a 205 case. We swapped the Chevy output off the CUCV for the Dodge output (on the T-case), then the 205 to GV adapter goes on and the GV OD unit is the last thing that bolts up. Yours sounds like a 2WD unit that bolts to the TH-400 and would be the last piece before the driveshaft.
If they have in fact retooled, call and try to get an adapter for your 205 to the OD unit. We went with the Dodge output for two reasons. First, we already had it, second, the Chevy output and adapter is a mile long because of the slip yolk assembly.