I'm assuming you have a 1300C, since that is the only VTX with a 19" front wheel (Chad, you should've known that
). The 1300 front spoke rim off the S model is 17", and I believe the rear is still 15". I think they should fit, but you may have to get the S front fender, too. Not too sure about that one.
Also, if you haven't done so, signup over on
www.vtxoa.com and ask your question there. That place is filled with all kinds of people all over the world, and you'll probably get alot more responses there than here.
Are you wanting white walls for your 1300C, or are you definitely thinking of switching wheels?