coil-over in an RA40 would require:
-removing lower spring seat from front strut assembly
-welding on threaded section for lower (and adjustable) spring seat
-new upper spring seat
this is all do-able but not without significant cost.
most folks with RA40's (self included) tend to restrict suspension enhancement to:
-nolethene bushes (or similar)
-better shock inserts (for the front) and shocks for the back
-better (usually lower or different rate) spring for front/back
...and often address the braking capabilities of the front disks
improving rear brakes requires adapting a different diff to the RA40's suspension mounts - again do-able but at significant cost.