as i recall, heavy lift helicopters have a range of payload from about 10kips to 40kips. the largest helicopter in the world is the sikorsky ch-54 'skycrane' no longer manufactured, but still in use for heavy lifting. some helicopter lifting sites on the web.

You have probably found your answer by now, but this info may be of use.
We have used ex-Russian helicopters for installing cableway components to difficult locations.
The MI-5 can lift a nominal 5 short tons and the MI-8 can lift a nominal 8 short tons.
The actual lifting capacity of a helicopter also depends on the conditions - if it hovers in one position for some time, a large downdraught (like a reversed tornado) is created and the available lift is much less.  The reduction in lift is greater when it is at greater height above the ground.