Tim Eichhorn at MPR Racing Engines in Boynton Beach, FL built mine. One other I would highly recommend is Tony Bischoff at BES Racing Engines and they are in Indiana, not too far from your neck of the woods in IL.
BES Racing Engines or Livernois would be my top picks....with that said MMR built a nitrous motor for me a few years back and it ran great......with all the negative info ive read on L&M Engines from a recent thread i wouldnt drop of my John Deere to them based on this customer's review and service alone.