SFX chopped off heads

[chrisBN]

Hi all!
I am currently developing a horror film that includes a sequence in which four chopped off heads are placed on stakes around a table.
any ideas on how to produce this scene as cheaply as possible?
i know there are firms that make these plastic heads, but they tend to be quite expensive, and i only need them for 2 shots anyway.but on the other hand i want them to look as realisitc as possible.

I was also thinking of using digital FX and simply "cutting off" the bodies of real actors in a kind of bluescreen effect. has anyone had any experience with fx like this?are they difficult to do?

[redlum]

I would have thought you'd be ok with your second idea aslong as you dont have to track them, and they dont mind being painted.