A good place to do that is countrycat.com. You can bring up a parts diagram for your machine to get the OEM number of the CDI Box and then compare different years for a match. Its always best to go by the OEM number of the part to cross reference.
Mike
If you have just 10% leakage, I wouldn't bother pulling the heads. It's a p.i.t.a. anyway. If any of the valves were bent, you'd have 100% leakage.
I think I'd just replace the chain. Retime the cams and call it good.
Are you looking at some online that are used? Whenever a question like this comes up, it's difficult to answer unless you have someone who has gone through the same thing. I usually suggest you look at parts manuals or OEM arctic cat websites and start comparing part numbers for various models and years to see if they match.