The only way to gain so much ride height is to remove the rebound springs and fit a short thick rubber 'washers', maybe 20mm thick, as opposed to a 66mm or 86mm rebound spring. There are some bump and rebound stops on the www that might be able to be cut to suit. This is what those who fly their Morgans on off-road trials do. The car will look odd though...
NB You will get much more bump steer if you significantly increase the ride height, particularly with a steering rack.
Regards PJB.
