I know this photo doesn't help a lot, but the one in the -4 I had was mounted under the floor. You can see the motor just to the left of the control column mounted to the left bulkhead. The rest disappeared under the floor and I don't remember what it did at the back end. Unfortunately, I don't have a photo of that area.
I installed the VANs option while building my -4. The kit is complete with all mounts and instructions. The flap control weldment is different than the one used in manual flap set-up, but the original could be modified to eliminate the flap handle attach point and install the drive arm for the flap motor jackscrew. There is also a second set of nylon pivot blocks with the electric set-up. All components are under the tunnel floor. Jim's set-up works just as good, and I have seen several set-ups in the side panel, which may be an easier retrofit. Either way, some re-work has to be done, but nothing major. here are a couple pics I have of mine from the build days.