I was just looking on scca's website as I am intrested in running my 325i in my local solo events but was looking at the clasification and it shows the 325 as being "not eligible" for the stock class. Am I missing something?

I'm not sure where you read the 325 being not eligible for stock.

Welcome to autocross.
The car is eligible for DS, STS, and DSP for starters. The primary difference is the amount of prep that's permitted.
In general;
stock allows struts, not springs, cat back exhaust, brake pads, air filter, rear swaybar, and race tires.
STS allows struts/springs, cat back exhaust, cold air intake, different seats, front/rear swaybars, but street tires (can keep cost down).
DSP allows a lot more and is primarly limited by your pocket book.

Take a look at the rules and where you want to go (how far you want to go) with the car and start planning. If your new to autocross, I'd recommend staying in the stock class, but forego the racetires. Most regions have a street tire class where everyone is on street tires.

325 M Technic isn't stock class legal. You're fine.