Based on the research I have done, I concluded Circle D Specialties or Precision Industries are top converters for the 5R55S. I am likely to go with Circle D as well, but am not ready to pull the trigger. Please keep us posted on your install and results?
Circle D installed seems to be a much better converter than the TCI
13 GT Premium, Track Pack, Procal, GT500 A/B, Resonator delete, JLT oil separator, Comfort package