For starters, if you have a FACTORY Z0K, there may be a badge on the back deck as the 2.4's have been seen with. The car will be noticeably lower than other Sols. Others that DO have Z0K stuff installed on their cars can weigh in on this, but since the sway bars are stiffer they they are probably bigger, so check to see if the front bar is more than 33mm think. The springs probably have part number tags on them. Verify the part numbers. Unless you know what the two different rear chassis rails look like that may not tell you much. There is an I/D tag (sticker) somewhere on the car that is 2.5" X 4" and lists the VIN and ALL codes for components on the car. If your car is a factory Z0K (fairly rare) then the option code will be on that tag. Otherwise, you simply have to get under the car and look for part numbers. If you bought it new and the code is not on the window sticker you don't have.
Wait !!!!!!!! That last sentence is the key. Call the dealership, (any GM dealership!) give the parts department the last 8 of your VIN and ask them to check GM's data base for the presence of that code on the build data.
Something above should get you the answer you want. HTH.
