Thanks Gary,
I'm keen to see how they go myself. From talking to a few pro engine tuners down here the cats don't have much affect on HP and might have a few benifits other than emissions. One that I can think of is that they would act as a flame trap and stop exhaust flames on deceleration. This could be a good or bad thing depending on how you look at it
I agree, the traditional cat converter isn't the pretiest looking thing to have in your engine bay. I can't imagine the shorty headers help performance either. The header manufacturers were reccomending between 28" and 34" primaries for my LS1.
Don't let my wife hear you mention GT40 or Daytona. She knows I'd love to do one or the other but would probably kill me before I laid a spanner on one.
Cheers