MK number for SINCGARS MK behind Pass Seat?

I have searched and searched and cannot come up with this info. Most of the FMTVs I have seen have the radio mount neatly tucked behind the co-driver's seat and not in the center position as required by the MK2400 and 2715 mounts. What is the MK number of this mount? Who has one for sale? And what is the purpose of the rectangular bag hanging from the roof? I bought one of those (ebay) but cannot figure out what goes in it.

Bag holds co drivers NBC gear,256 kit and first aid kit the stuff that went in the CD's box that was removed for the radio mount. #98