Probably won't work, because the track width is wider on the s550 than the s197 by over 2" I think. You'd end up hard pressed to put a decent sized wheel and tire without flairs. I've thought about putting in an irs in mine, but using the art Morrison IRS or Heidt's universal irs. I know the Morrison is available in three different widths. With either you are looking at $10k easy.
S550 IRS in a S197
Threaded Mode