I have koni yellow (S4?) rx7 inserts in my capri struts in the RS. They are quite a bit shorter and i have shortened the strut by 50mm as my car is VERY low, but this does not have to be done. The strut top will need modifying to suit the different size shaft. There is a single bolt that is goes thru the bottom/base of the strut tube and into a threded boss on the botom of the shock to hold it in place. I dont know the part number off the top of my head but i think i have posted it in my project thred somewhere[B)].
They seem to work very well with the limited testing I have done with it.

If you have a bit of money to spend, ring toperformance and get a price on their koni double adjustable strut inserts. I think they were about $800 for a pair for memory.