I believe it can do done, yes. I guess what you mostly need is for the loops at the neck part in the body and the neck part in the head, to have the same number of vertices, so they have to match in quantity. If the loop around the neck head has 20 verts, then the neck body should have 20 verts in the loop as well. If not then there's some serious re-modeling to do to to get them to match. Of course you could do some of the tricks of 4 edges to 1 and all that thing, but I guess you should have messy topology in the neck if it's going to be rigged and animated.
Thanks for the reply although I'm still wondering. Can I keep the details (such as pores, wrinkles and such) combining a head to another rigged body? Because when I join the head with the multires to the body the multires seems to stop working and I lose those important details. Sorry, it's a bit hard to explain it