There is a V.35 module available for the ATLAS 890. It is part number 1200184L1 and comes with 2 dual DB-37 adapter cables providing a total of four standard V.35 Winchester female connectors. (https://www.adtran.com/pub/Library/Data_Sheets/Default_Public/ATLAS_800_Series_Quad_Nx56_54_Data_She...)
As far as compatibility, I'm not aware of any V.35 DTE device the ATLAS is not compatible with (the ATLAS is DCE), but I'm also not aware of any testing specifically with the Cisco 3340, or MCU 5320.
Hope this answers your question,