I keep coming back to that forklift.

If you have hard ground for the forklift, you should be able to dig or
excavate by hose tunnels under the rock, rig two basket slings, and do it
that way.

If I had to absolutely do it myself, I'd build a trailer with rails at a 160
angle, or thereabouts that could be stabbed under the rock, then a long
tongue to apply leverage and lift the rock at two supporting points.

I had actually thought of that after I moved that one rock with my ATV
trailer. Making it a leverage thing where you backed up to the rock, hooked
up to it, used the leverage of a long tongue and short boom to lift the rock
just until it cleared the deck.

I'd like to jot down some of the ideas I have one of these days, and post to
flickr for comments.

Steve