OK, so I did some spring measuring, and compiled some notes from all the spring sets I've measured.
You will find the spring force at installed height (38mm/1.5in), force at bind and bind height, max lift (bind height +1mm), spring rate, and spring force at 12mm lift using a 38mm installed height. Now you can move the spring forces around with spring shims and playing with the installed height.
Stock small diameter spring: 55-60lbs @ 38mm, Coil Bind: 200-210lb @ 24.8mm, max lift ~12.2mm. Rate: ~265lb/in. 185lbs @ 12mm lift
Retainer/spring mass: 18g, 40g
Stock MID diameter spring, OD 29mm: 70lb @ 38mm, Coil Bind: 200lb @ 24.5mm, max lift ~12.5mm. Rate: ~243lbs/in. 185lbs @ 12mm lift.
Retainer/spring mass: 19g, 48g
Old RSI(?) single spring and Large dia OEM retainer: 135lb at 38mm, Coil Bind: 280lb @ 22.6mm, max lift ~14.4mm. Rate: ~240lb/in. 250lbs @ 12mm lift
Retainer/spring mass: 21.4g, 48.8g
Single Culberro Spring: 110lb @ 38mm, Coil Bind: 230@21.3mm, max lift ~ 15.5mm. Rate: ~210lb/in. 210lb @ 12mm lift
Retainer/Spring mass: 19g, 46.8g
Yoshifab Beehive: 108lb @38mm, Coil Bind: 240@24mm, max lift ~13mm. Rate: 240lb/in. 220lbs @ 12mm lift.
Erland Cox Dual Springs: 100lbs @ 38mm, 275lbs @ 16mm lift (bind is 19mm), Rate: 275lb/in. 230lbs @ 12mm lift
BTR SP008: 70lb @ 38mm, Coil Bind: 275lb @ 22.1mm, max lift 14.9mm, rate 330lb/in. 225lbs @ 12mm lift.
Spring mass: 38.6g
For BTR SP008 use Ferrea retainer #E12014, will need to find lower spring seat or use small diameter Volvo spring seat with excessive play.
I'll weigh some retainers and add their weights later on. If anyone has the weight of the Yoshifab retainer, that would be great!