I fitted SSL to my old +4 from 97. The car was far better but also had new king pins , bushes & shocks so it should be .I'm neither a fan nor a critic but I would now go the shock & king pin route first.
My Roadster has adjustable shocks and is fine for me. I have driven cars with SSL front & rear the rear is definitely stiffer & more placed on bends but I don't find it better just different. Others on here will have the opposite view.
I would try to find a local owner with the full or partial SSL who will let you test drive before you buy. Nut also be aware MMC changed the steering geometry so later cars are just better.
Also do the basics first. Brake reaction bars are very cheap & really stiffen the front.
Fit a panhard rod etc
