might have better luck posting this in a tech forum....this is the for sale forum
the conversion kit should add 1 3/4" to your overall track IIRC, so figure on about 1" per side. you can keep your wheels and not worry about it, you can keep them and get spacers for the rear, or you can get 2 new rims with 1" more BS. i wouldnt reccommend the last idea, solely because its too easy to mismatch the rims with their proper location.
-Bennett