guys and gals,

if you were given a 1/8 scale 4x4 buggy free, what would you choose for the engine? This things a little heavy so I want to overdo it in the powerplant department for pure fun factor. I have plenty of space and can fabricate pretty decent too.
Just want some ideas for which engine to use. This thing is a vintage Robbe Pantera aka Great Vigor/Hobby Lobby Hunter. built like a tank.

What would you use? Keep in mind, I'm gonna need an engine cradle or mount which ever you call it.

Thanks guys, and sorry the pic is huge.