I'm pretty sure we'll have to modify the headers to include a high flow cat or have a set custom made with a high flow cat. I've looked at pictures of the headers available and the 4-1 designed ones look like they'd be easy to add a cat to. Depending on how much you want to spend I think I may have found the perfect muffler to custom mount
It looks like we're both going to end up doing a top end rebuild. We just need to figure out how we're going to do the cams since you need hardwelds or regrinds. Hopefully I can replace my timing belt while I'm at it. Ben told me it's not too hard if you have the head off anyways. You should look into picking up a second cylinder head so you can do some porting prior to installation.