Sounds like fun prime. Make the suit as lightweight as possible. As for being 8' tall, you may want to consider 7' as this will seem menacing enough against actors who are usually around the 5'8" average.
I say this because with any type of stilts to boost the actor up, (who must be in good shape and around 6' to handle it) will have to function properly in the case of any running or heavy action.
Also, think about the awkward look an 8' monster would have with normal length arms. (unless they're longer than normal like mine) or maybe some type of arm extension.
Maybe you could rig a couple of those plastic toy arms that have movement from a grip that you pull.
Again though, the main objective I'd say is keep the suit lightweight.