^what he said.
And like I always say, find what works. Lots of people here have found good numbers that work for specific applications.
The 240Z handles nice stock, the 240 Volvo, NOT.
Yep, definitely odd frequency front to rear, but it is what it is.
I mesured how much pressure it took to compress each spring, and retested each run. Then I increased the pre-load, so I got numbers starting at 40, 50, 60, 70, 80lbs. That's TEN tests per spring.
I will have turbo wagon (US) from the junkyard as soon as I have the money to pay for the front suspension. Until then, nobody has offered to let me test any springs at all. I do what I can.
I'll test another mid-80s sedan soon, and also a non-turbo 940 wagon.