I found some info on the May 2019 Indy Car Pack on GTPlanet - Forza Motorsport 7 May Update Introduces Indy 500 Cars New and Old – GTPlanet
Representing the Chevy camp, racers will be two Team Penske cars. Moving to the Honda cars, Chip Ganassi Racing and Rahal Letterman Lanigan Racing. Coupled with the high downforce of the Universal Aero Kit, all four cars will provide some serious fun.
** If you want to swap nose and tail to the oval aero kit, that too is available in the garage - GTPlanet **
I actually found the oval aero kits in the Tuning & Upgrades tab in the Upgrade Shop in Aero and Appearance to be purchased. Hope this helps with some of the racing fun for now. Can’t wait to see the feedback and comments on the June 2019 Forza Race Regulations updates.