If you are doing this on a mk2 or mk3 all you need is 2 hockey pucks. Drill out the center so it fits around the shock and put it on the shock on top of the perch and then put the spring on top of that. It won't work on a mk1 because the spring diameter at the bottom is too large. The car I did this on has been running for at least 2 years now as a delivery vehicle so it gets a lot of miles.
Unloaded the ride was pretty harsh but I was using mk3 VR6 springs and shocks in a mostly stripped mk2 Golf. I think I had mk3 2.0 springs in the front. When I had a load it was much better. I regularly towed a trailer or hauled an engine in the car. Usually the engine rode shotgun with the seat removed but that wasn't always the case. I think it would be a lot better with the stock springs. Now that the springs are a lot older, and the guts of the car are put back in it, it's not bad, still stiff though.
would you suggest mk3 springs for the back of a mk2 that often tows?