Rocket Bunny widebody kit offers no adjustable front aero in Forza Motorsport, nor any front bumper upgrades to make it adjustable. Forza Horizon 5 has same car + kit and it offers adjustable front aero, with no additional parts.
Additionally, the Rocket Bunny rear wing is classified as Sport in FM and is non-adjustable, but in Forza Horizon 5, it is classified as Race and is adjustable.