Adjustable Spring Perch- Stock 510 Rear Mount

[jeffball610]

I'm having trouble finding any info on spring perches for the stock PL510 location. I know someone has done it, but I can't even find good info on spring size. From what I can gather, the stock rear springs are about 4.25" OD and about 3" ID. The suspension kit I ordered 10 years ago from Top End Performance is no longer available, but works pretty well so far. I need to adjust the rear just a bit due to my Z31 spindle swap I did.

 

I've searched for perches, but info seems thin from what I've done so far. There are some kits for 5" springs and lots for the common 2.5" springs most of us run on the front struts. Does anyone have a decent source in the states? I'm trying to get this resolved before this weekend 6/3/17 so I can make the most of my first autocross event in the car.

[jeffball610]

This is what I'm currently looking at, but it states it's for 5" or 5.25" springs. It also says it has a 2.75" ID which would probably be too tight for a 3" ID spring.

 

http://www.speedwaymotors.com/AFCO-Adjustable-Spring-Spacer,49203.html