That kind of has me confused, because the Indy 500 motor has been around a lot longer than the XC 500.
But it could be because the XC 500 is considered a "high performance" machine, and the Indy is considered a "trail performance" machine, so all the companies figure they will make performance parts for the high performance sleds instead of the trail sleds.
That's what I think anyway.
Hot seat has performance parts for Indy 500's though, at least clutch kits, I dunno about pipes and stuff though
http://www.hotseatperformance.com
http://www.bolliger-mabillard.com
I Love B&M Coasters.