Hi all, car is approximately 2100 lbs, with 1100 lb on the rear wheels Shocks in rear are shot, probably the springs also.
The springs in the car are about 12.5" free length, non adjustable.

I am thinking maybe 140 lb springs in the rear, with Koni adjustable height shocks, Car is electric. I don't care if it is a bit stiff.
Any suggestions?

Running 140 lb springs in back with Bilstein's and 19mm torsion
bars in front. Nice firm ride, not too stiff.

Step up from stock to 100lb is a huge gain. It's what the geometry of the suspension suggests would be optimal in a stock configuration.
If you are running a larger (heavier) engine the 140/160 progressive would be the ticket. If you are pure track you could go heavier, but wouldn't be a comfortable street ride.

https://914rubber.com/search/?q=Rear+Spring+set