They should do as I can remember quite a few years back I'm almost sure when my brother-in-law rebuilt his series three he used long wheelbase heavy duty springs and coil over shocks.
Will fit, used to fit standard duty 109 with assisters to 88" models, not too stiff and pops them up a bit assisters come in to play when heavy trailer on.
That was my brother-in-law, not me I did find it a bit of a strange set up I would have gone for standard, heavy duty or gas depending on what ride you wanted or your intended use i.e. heavy trailer towing etc