I'm thinking about giving him a furry backpiece to fix it, but if you want I think you could just chop the head and hand off a Mauler and use that instead. The conversion rules seem to suggest that as long as a character uses all the upgrade bits you can put it on whatever body you want.
I really like the Bomber and Blitzer, but I don't want more than 2 beasts with the exact same body. I like Trolls because none of our beasts look swappable, so this kinda goes against the grain. Remember though, we have to compare it to the other Troll heavies which are some of the best.