E30 Coilover Ring Seat K0040 is in stock. It goes into detail on

It goes into detail on the swap so that any shade-tree mechanic can do this swap in less than 1 month with a $1000 investment (assuming they have the car and drive-train already acquired)

You could always get the "Weld it yourself" Dssr found here

an E30 shock insert will fit inside the housing

The benefits of the DSSR are explained below:

E30 Coilover Ring Seat K0040 is in stock. It goes into detail onBMW E30 COIL OVER RING SEAT Description Though this kit may seem basic to some, it is crucial for the proper installation of coilovers on your E30. This kit is meant for coil overs that are designed to sit on the stock spring perch. This E30 coil over ring seat kit is Ideal for a cleaner install and adds a proper seating area, instead of just sitting on the stock perch weld. It's a must have if you relocate your coil over seat into a different