I made some pictures while building 5 of these newly "bred" Dire Wolves, though it's not really a tutorial.
And since i'm no sculptor, i actually don't know how to exactly describe every step on the sculpting, so i just hope you guys get an idea while viewing the pictures.
First cut the headpieces as shown and trim off any excess plastic.
Drill two small holes both into the "neck" and the new head, glue a paperclip (or any other suitable wire) into the neck's hole.
Clip off the paperclip as shown.
Testfit the head onto the "pin", but don't glue it!
Take a small ball of GS and press it onto the pin. Now put the headpiece onto the pin too.
Use a moistened tool (i'm using a small spatula) and spread the GS between neck and head.
Trim off any excess GS and try to create a furry texture by dragging your tool firmly in direction of the hairline from the neckpiece.
Repeat this step until there are no more flat surfaces, but keep your tool moistened!
After priming, it looks almost as if the Wolves were intended that way.