Yes, STU is for coupes & sedans with at least 4 seats.
http://scca.com/_FileLibrary/File/St...nufacturer.pdf
STU
Coupes/Sedans - 4 seats minimum except sports car-based
Engine size (maximum)
- unlimited normally aspirated or
- 3.1L forced induction (single turbo/supercharger)
STS, STX Rules plus STU allowances/restrictions