So in my search for correctly rated springs for the GS450H I was coming up empty. I apologize for the multiple posts and pictures. This information is what I had wished was available and I hope to help a fellow enthusiast that are looking for GS450h springs.
I saw that there are many here with Tanabe DF210 Part# TDF112 and NF210 Part #TNF112. This spring is well documented here (Thank you Stormforge, Mike@vossen, and whoever else I missed!) was designed for GS300,350,430,and 460 models. TNF112 Spring rate= 4.6Kg/5.8Kg, TDF112 Spring rate= 4.7Kg/6.1Kg according to the Tanabe USA website.
I did not want to compromise the ride by having springs that are way too soft for the rear of the GS450H. As many here know, and now you do too, the GS450h has it's hybrid batteries in the rear of the car. This adds a significant amount of weight to the rear of the car. This means the spring rates that work for the non-hybrid models will not work for the hybrid. That is to say, they were not designed to handle the load. I would say the easiest way to visualize this is that a GS450 with no passangers is like a GS300,350,430,460 with two passengers in the back seat.
So I began my search for properly rated springs for the 3rd gen GS450h. I had reached out to Eibach, and Tanabe USA. Eibach has not responded once. Tanabe had responded and requested to use my car as a test vehicle. The test procedure was not very transparent, and with no benefit for loaning the car I decided not to go that route. Mind you they were very responsive and explained everything I asked them in as much detail as they were allowed to. Since I am lucky and have contacts in Japan I decided to see what is offered in the market there. Low and behold the first search came up with Tanabe NF210 part #GWS191NK designed for the GS450h 06'-12'
Now the spring rates on these are as follows: F4.5Kg/R7.0Kg drop rate is quoted as 15-25mm for both front and rear. Needless to say, by numbers it looked good so I ordered from amazon.co.jp and had my contacts ship me the springs.
Thank you to SONIC MS in San Jose California for doing the install. I highly recommend this shop.
Type: NF210 Kit
Front on left. Rear spring on right
GWS191NR stamped (rear spring)
GWS191NF stamped(front spring)