Welcome to the club. Good to see you here.
Would you know the weights? Front & Rear? Or have you ever had the car on any scale? If you have the combined weight, you can rough estimate the front to be 60% of that number and the rear 40% of that number. The next question will be what is in the car now for springs? Are they coils
or leafs? There are also estimators at sites like Speedway / AFCO, for the coils, those will get you into the ballpark and you can always replace with a firmer or softer spring once you establish where it is now.