Hi Nigel
Thanks for the vote of confidence, remember I'm just a dumb carpenter the people who built Stonehenge where experts at moving stones (they lived in the stoneage) regarding your question how many? I reckon as few as 40 men could move a 40 ton stone, however many hands make light work. With more manpower the fulcrum logs can be positioned further away from the stone resulting in more distance gained with each lift. A lot more work needs to be done to find the best solution.
Regards Gordon