Don't do it
A couple of years ago I was involved with building a set of prototype MR dampers for our race car. Wow what a job that was - you need to be extremely accurate with the machining and work to very fine fits/tolerances. All the seals need to be correctly specced (we had problems with the MR fluid eating seals) and you need to get the correctly ground piston rods. Add to that the fun of machining a very fine thread on the outside/inside of the shock/spring seat combined with getting all the tolerances right for hard anodising. We must have been a good week of 12 hour days, jigging, machining, programming etc. When you realise how much work goes into a set of dampers then £85 each is a bargain.
It's the dampers that keep the car firmly planted on the road so they are a worthwhile investment.