I picked up a headless KO classics Megatron recently.
Then I picked up a deluxe animated Megatron which was missing his thighs.
Result:
Rest assured I will be painting this bad boy to make it look a bit more unified. Plus the head is too big to fit into the chest compartment. I'm undecided whether I'll shave the head down or just make it into a parts-former.
The balljoint on the animated head was also too big for the socket on the KO. I dremelled it down too far, so I've used tissue in the socket to make it a tight fit.