if its going to be smog legal, you'll have to go with a 97+ ex engine, which means a y8 engine. Z6's are the previous gen, and cali's carb laws are strict as fuck. If you use an older engine, you WILL NOT PASS inspection or whatever the hell they do.

You could just swap the head and do the "mini-me" swap, but if I was going to do anything with it, I'd just swap the whole y8 engine. $.02