I just picked up a wheel with a shimano FH-M510 freehub. Google has told me that this is a 8/9 speed freehub. Unfortunately I _don't_ want to upgrade my 7 speed shifter and derailleur. I have a nashbar 7 speed cassette which fits loosely (i.e. completely unusable).
What is the cheapest and easiest way for me to get this wheel working on my 7 speed bike?