The set of Proflex shocks I found came from a tarmac rally car, so they have pretty stiff springs fitted. There are no markings on the springs anymore, so I measured the length, thickness, number of coils etc. so I could estimate the spring rates. For the fronts it is somewhere around 90 N/mm (515 lb/in) and around 55 N/mm (315 lb/in) for the rears. I am planning on using front springs of 60 N/mm and rear springs of 30 N/mm, so the valving of the shocks needs to be changed too.

Since I like doing stuff myself I went looking on the internet to see if there was some info on how the Proflex shocks come apart, and yes there is:

And it doesn't seem so complicated either.