Grand Stand Designs has a 240mm tire kit. There are a couple guys on here who have converted to the 240.....Onelogue being the most recent.
Here's his build thread:
Onelogues 240 rear thread
Grand Stand Design's website:
Grand Stand Designs 240 Tire Kit
Here's my thread on chain conversions. Not a 240, but still good info on parts, part numbers, prices, etc outside of the GSD kit.
My Chain Conversion Thread
This should get you everything you need.