Yes I also have a Mustang but sorry, I can't help you. 4 cylinder engines are not my specialty. A great place to look for parts is Ford Racing Parts.com . Even if you don't buy from them, you can get the catalog and narrow your part search down pretty well. As for your car, if I were you I would first start with weight reduction before you move on to engine
mods. Getting rid of excess weight makes a big difference. How much power is your engine putting out? Is it worth trying to find a cheap V8?