Need help, cutting the neck off a head and mod to fit a muscular body...

So, the title pretty much says it all...
I need to mod a regular head into a neckless one...

Basically turning this:



Into this:



I have a spare neckless one to use the "neck-hole", but I'm wondering if I should just cut the neck with a dremmel?
And how hard would it be to "finish" the cut part?
Anybody has done anything like this before?

Thanks a lot!

I've only done it once and with a resin head.

I used a neckless sculpt as a guide and made a pencil line around the jawline, under the chin and back of the head where I wanted to cut. Used the dremel to cut a little BELOW that line, then sanded with the dremel carefully up to it to keep it 'finished' looking. You'll be nervous as ____ first, but once you get a hang of it you'll be fine.

I didn't used a 'neck hole' though. I just drilled and dremmeled the hell out of the inside of the head itself to fit the neck of the body.

Turned this headsculpt:


Into this:


And painted: