Amarin wrote - "So that leaves spring #6819404 and #6819405 as HD variety. Even if #6819404 installed as standard in 940 sedan, it must have been coupled with soft damper/absorber to balance it out."
From my experience it doesn't work out that way. I base my opinion on having monkeyed with spring and shock combinations with both 140 and 240 series Volvos to accomplish carrying capability and general handling. When I purchased my 1980 245 it had been used for towing a camper and family vacations. It had overload springs (larger wire diameter) and brand new standard Volvo shock absorbers. What I found was the car had uncomfortable gyrations before settling down over bumps. I had a set of HD Bilsteins on the shelf so went ahead and installed them. That took care of the gyrations but resulted in an extremely stiff ride. I went to a later standard 245 spring (larger wire diameter than standard 1980 245) and that, with the Bilsteins, was a happy medium. I'll say this--it took a lot of crawling around under Volvos with my dollar store plastic caliper to gather info. :-) Dave