Ah I see, so the grey plastic parts are all reused from the originals but are swapped around between the robots. Growl's chest is the same as Flak - the grey part. The stomach and hips are a different piece on both. Cratermaker and Bombshock have different heads, Bombshock's is much bigger. They're the same design but it looks more like Cratermaker got a rejected prototype. Bombshock's is much better.
More FIDDLING is needed with this. It occurred to me this morning that Trip Up and Daddy-O are basically the same figure with different parts, so one is a heavy remould of the other, but they are both derived from Swindler - same proportions and engineering with a single change in the way the bonnet hinges.