Good morning, driver side front (Right hand side if viewed from rear or off side front if your technicle) is approx 20mm lower than opposite side. Springs and shocks are new. I plan to insert a shim on top of spring to adjust the ride height. Any idea on shim width to adjust height by 20mm ? Is it as simple as 20mm, surely not ?

 

I had a bent shock once. The car would be stuck down on one front corner, and wouldn’t ‘bounce’ when I leaned on the mudguard/wing panel. Thought I might have a broke spring, but it was a bent shock...
you shouldn’t have this problem if all new parts.
another time I crashed my car into another and one of the big chassis beams that run forward, and have engine and suspension bolted to them, was bent down about 2 cm and had to be straightened...
it will still do 120mph, so it is all fixable!