I know I've seen leg and now arm pics, the only thing missing is the core body.

I think the reason why they're using FeralRex's fist is because they haven't designed one of their own. Since the the throttlebots don't originally have a gestalt form and its just Toyworld making it a gimmick so you'll buy them all.

I'm assuming Wide Load will act as the Long Haul and Goldbug will be the upper chest.