If you wanna do that, buy a universal O2 sensor. They come without the connector(I think they do come with some splices, though). The ones that I've seen have been more expensive than the non-univesal ones by about $20 for some odd reason, but if you're REALLY cheap it only takes a pair of wire cutters to convert a 3-wire O2 sensor for an '88 Mustang or a 4-wire O2 sensor for a '95 Contour into a universal one
Brian
