see it you can find some sort of large articulated Triceratops! lol Or Palisades Birkin if money is no object on this onealso maybe just switch the pelvis down from a rotocast venom.
mhh it's really complicated if what you want is to make him in 6"scale I can only think of those cheap plastic animals that you can find anywhere, since those are made in many scales but to make this custom I think it would be impossible to avoid sculpting, it would need LOTS of sculpting for sure
Japan Obitsu the DOG Body Assembly Kit 1/6 Size Plastic Figure White