The Morris Minor centre in Birmingham do a bolt on kit which uses your original top mounting and a different spring plate.
I understand they offer a large improvement on the original items, but it all depends on how good you actually want it.
I have used turrets welded through the floor and re-enforced with a piece of box section (in-between the turrets) which is also welded to the diff bump in the floor. But this route takes a fair bit of work and a lot of welding, but as John says, it is good because the shockers are vertical and as close to the wheels as possible.
I am very pleased with the results.