So going with the idea to work on each piece individually and then “Attach” everything, I built a nice looking mouth while trying to have the “hanging” skin off the side like a dog.
But this is where I’ve come to a problem, I can’t get the mouth to attach right, not even to a simple box.

AutoDesk 3dsMax9 SP2 Educational version
Mobile Intel(R) 945GM Express Chip/96 DPI
1920x1200/32 Bit

	Attachment

For every vertex on the mouth (at the point where the mouth meets the head) you need a vertex on the head as well.

Try this. Create a box for the head but with sufficient segments so that the number of vertices match those on the back of the mouth. Convert to poly, delete all the polys on the side of the box which is facing the mouth, do the same to the end of the mouth if there are polys there. Select the 2 borders (the open edges created by removing the polys) and Bridge them.

Probably won’t be perfect but should be a reasonable starting point.

Max 4.2 through 2013.
XP-64 (SP2)
NVidia 9800GTX-512 (Driver 266.58).
Core 2 Quad Q6600 2.4GHz, 8Gb Ram, DX9.0c.

Was modelling the individual parts the best idea? It may keep leading to this kind of problem if you don’t think it through.
Here is a dragon modelling tutorial you may find helpful.