The most famous representation of the Chimaera is the Chimaera of Arezzo which dates back tho the fifth century and is probably the most original of the image conveyed by Hesiod in his Theogany which describes the Chimaera as a lion in the forepart, a goat in the middle and the hindpart of a serpent with a gaping mouth that vomits flames.
Personally I find the Chimaera as one of those mythical monster that is most difficult to assemble due to its unusual composite of various creatures in one body. It is pretty challeging to draw three different head of different creatures and splice it into one single monster, that is why I seldom have monsters with three different heads. Though the bronze Chimaera of Arezzo is very famous, the depiction of a goat's head sticking out in the middle of a creature's body is rather awkward to me. I therefore decided to take the easy way out by drawing the other option as some medieval writers have also describe the Chimaera as having the hind-part of a dragon in spite of the serpent.