I built the S Model Ram sometime last century and it's severely mishapen, as are the Verlinden and H&K conversions. It looks to me like there are side hatches on the tank in the foreground of the photo and the Commanders hull matches that. I have the Commanders conversion and it's far better than the old S Model kit. If you have the Formations OP then you've got the turret you need and all you'll really need to do is make a "horse-shoe" thingy for the mantlet and find yourself one of the many after market 6 pdr guns. Commanders+Formations+Dimmick=
I've always loved that picture myself!