Pat,
There isn't really a rule-of-thumb for this. Your best bet is go here:
http://toy4two.home.mindspring.com/offset.html
Plug in your base specs and compare to the wheel you're looking at. You need to measure the clearance to the strut tube with the stock configuration to get an idea of how much clearance you have to work with. And remember, always test fit and verify clearance before driving!
