Like everyone has said I think that 4s 8000mah is a good place to start...
I would go for a high torque outrunner in the 800-1000kv range...
Check with john but this might be the ticket.
http://holmeshobbies.com/product.php...&cat=19&page=1
or
http://holmeshobbies.com/product.php...&cat=19&page=1