It seems you can run 89-90 ka24e(single cam 3valves per cyl) only so u might not have the 91+hicas option which are only on ka24de (twin cam 4valves/cyl).
10. ENGINE
Must be stock for make, model and year. Maximum engine size is 2500cc. No rotary or multi-cam motors allowed. Maximum 3 valves per cylinder. Stock cam (duration and lift) for the engine installed.
yea but when they measure springs all they measure is number of coils and coil thickness. so what makes these 91-94 hicas springs different?
dunno about coil count OR thickness differences
but i believe the free length is different for the hicas springs
the fsm gives some specs, check it out
do they look at the rear anti-roll bar? you could consider putting in a rear hicas bar (21 compared to 15mm) and banking on no one noticing/realizing 
then again i dont even know if a bigger rear bar is desirable for your situation
or a skyline rear swaybar, thicker than hicas one COUGH no one notices COUGH
i’m not too sure about the rule on swaybars as it isnt very clear, it says no adjustment but does not state that it has to be stock. however it states that suspension must be stock.
does anyone make swaybars out of a stiffer metal that would be the same diameter but stiffer than stock?