Verts can drop quite a bit when a hardtop is installed so this too needs to be taken into account. Another small item that makes a bit of difference is the rear spring pads. Again there were quite a few different thicknesses and as E36's like to brake rear springs these were often forgotten to be put back in. So check these also. The thickness of the rear springs pads is specific to the rear springs in the car. I.E 5mm spring pads came with white stripe rear springs IIRC and so on so fourth. Rear spring pads range/d from 3mm up to 22mm again IIRC.

As Rebel Ranter said there are quite a few options for rear springs and going through the ETK is well worth it to find the right option for your car as there is different part numbers dependent on year and model of E36 verts and if msport of non msport also. Springs will also sag with age so fresh items will help in numerous ways. Check also that your rear shocks are fresh and will be able to handle new springs, if you feel they are past their sell by date swap them out also.

If I get time I shall check what springs are on my 318ic vert as it is standard height M-Sport, if springs are original they should be color marked and this will at least rule out buying these ones.....that being said with the hardtop on it still sits nicely and not too low at all. When I run the Motorsport wheels with 245/40/17 rear tires and hardtop on it does not rub at all, when I run the Throwing stars with stretch 215 tires it does but I do know for sure my rear shocks are weak and if the car is still on original springs (which I doubt) then they will be weakened at this stage in their lives for sure. On the 328 with the hardtop on it I have BC coilovers and the rear does sit too low even when adjusted high, the rear BC spring rates are to week for the 328ic with hardtop (as they came from 318is coupe) so I am waiting to get time to fit the stronger rear BC springs.

Hope this helps.