The trouble is.. we have here in the netherlands english s30 serv.man with a american 240z in it. (surround lights, rozets on bumpers.. a euro does not have..) 

but here are some specs,

wire diam. 11,4 mm, coildiam. 100mm windings 10,65  free height 381mm  installed height 225mm   normal load 288kg.  spring constant 1,85 kg/mm.

Years ago i changed my rear springs because the orig. us. springs were to soft. (50 kg of sandbags and the exhaust came on the ground!) then i installed my spare (euro)  springs and they are much stiffer!

So now i think the 1,85 kg/mm. constant of the spring is for the US-spring, the euro spring is a lot stiffer? 

I do remember that on the fiche i could select 1 out of 5 different struts!  You could look for different springs on a fiche 240z..  

These are the specs that I have in my notes for the Nissan Europe springs that MSA used to offer (but now NLA, according to MSA's website):

Front: 122 lb/in (so +17% vs the NA-spec spring)

Rear:  142 lb/in (so +36% vs the NA-spec spring) 

 

For comparison purposes, my notes show Eibach's progressive springs with these specs:

Front:  133 - 183 lb/in

Rear:   154 - 212 lb/in

 

And the Vogtland springs as follows:

Front:  152 lb/in

Rear:    170 lb/in