The original (red) spring rates for the inboard suspension models 1, 2, 3a, were 170 Lbs/in and were too stiff so people changed them to around 120. One of the many things that RHE were inconsistant with were the spring colours, I bought 120s from them which should have been black but they were red too.
The geometry of your suspension with the more conventional? set up will be much greater than 120 Lbs/in. I have seen a Mk 2 car with external shockers like yours but whether there is an owner on this site with one and knowledge of the spring rates I wouldn't know.
Doing away with the roll bar and fitting tie bars makes a great improvement in the handling, Usually the roll bar is just bolted up from underneath but it almost looks as though yours is inside the monocoque?
Where abouts are you, and it's well worth joining this club for information and advice as well as getting a reduction on your car insurance!