That's an easy one...ST.
That is, unless you also have SVT rear brakes, which IIRC puts you in FSP.
(You mentioned SVT kit, which I assume is dampers/springs, but I guess it could be brakes too.)
Here's a hint on classing cars.
If it doesn't specifically state that you can
do it in the rules, then you can't.
Stock says nothing about springs, so you can't
change springs in Stock class.
ST says you can change springs, so you can
put on different springs in ST class.
But then again...
I see those aftermarket upper and lower grilles.
If there's a real diehard in your club, you could get bumped clear to EP.
(That's the first time grilles are mentioned)
17. PREPARED CATEGORY
17.2 BODYWORK AND STRUCTURE
A.Grilles may be removed,modified, or substituted.