I have made a bunch of M981s over the years. I highly recommend the Academy version. I have used the old Verlinden conversion set, it was a pain in the
a@@. Also converted the Italeri M901 ITOW to a FIST-V. These were before the Academy M981 was available. The Academy kit is great. Only thing you will need to add is the circular guards on the rear antennas. I made mine out of a piece of drinking straw, with the square openings carefully cut out. I have made a bunch of M981s as farewell gifts for some of my FIST NCOs through the years. They loved them. Here is mine that I made for myself with full interior using the Academy M113A2 and the Italeri M901 ITOW (before Academy M981 model).
I have also made an M7 B-FIST from the Tamiya M2A2. Check in my Showcase I and II below to see pics of it.