Hi:
I was a crew chief in Vietnam 1966-67 LVTP5A1....... The area that you are pointing to is the aux. generator. We reffered to it as "little Joe"
It was used to re-charge the batteries and for electrical power when the main engine was not running.
I have some nice pictures if you need them. Meantime I would likesome advice on building a Diorama of my "Trac"
Thanks..... Sgt. Jim Falotico USMC (lomg time retired)