Here are some picts for reference from two club members who made the upgrade. One kept the stock battery location and the other did not. Both used stock HL gearboxes. Neither of them added the recoil or flash.
Good luck!
(they post as pcomm1 & SCAT PATTON on the forum)
http://web.mac.com/ksoc/Special_Proj...anzer_III.html
http://web.mac.com/ksoc/Special_Proj...anzer_III.html