Sorry not a great answer but might be helpful. During "car wars" when the CART and IRL series were separate series, 1996 - 2000, the IRL raced at Las Vegas Speedway.

FSE had a CCWS (Champcar World Series) street race in 2007. The IRL and CCWS joined forces again in 2008, so that was not renewed.

2011 the new reunited Indycar held a race at Las Vegas Speedway which ended after 12 laps in a 15 car pileup where Dan Wheldon lost his life. Indycars are not really suitable for pack racing. They haven't returned to Las Vegas

The name Champcar was abandoned and is now owned by a private sports car racing organization that runs 8 hour enduros at various sports car circuits.