Okay, here's the breakdown...
There were two 18" Kong puppets, which had slightly different proportions as well as different heads. The first( the 'long' head, or poster face, as I call it) was used to shoot the test reel, which featured the log sequence and T-Rex fight. This was actually the third version; Merian Cooper had rejected the first two for looking"too human". After the test was shot, the model was used to shoot promotional pix. When it was returned, Coop had Marcel Delgado rebuild the puppet yet again, making it even more 'gorilla-ish'. When the film was finally green-lighted, a second 18" puppet was built to allow faster shooting and turn-around. This figure was machined by the studio metal shop, and was slightly different from the first( in addition to the rounder head the arms were slightly longer). Later a 24" puppet was built for the New York scenes( the 18" puppet 'wasn't big enough' on the NY sets). This figure was also somewhat different in proportions. Adding to the fun is the fact that, because they were built-up( instead of injection molded) their appearance changed every time Delgado re-built them, which was done @ every 3 days. The most noticeable change is the bulk of Kong's brow; in the later shots they are almost twice as heavy as in early footage.
Also built were the full-sized head, 2 hands( one a mock-up, one fully articulated), a foot and a 4" model used for the fall. Today only the original armature survives intact. The LA County museum has one of the 24" figures arms; the other 18" figure was dismantled and parted out. Peter Jackson owns the 4" figure, along with the Pteranodon, the Styracosaurus, and the Brontosaurus, along with many other small props and photo's...PS