I fitted these brackets to the front of my Mini and used standard lenghth Gaz adjustable shocks.
SHOCK ABSORBER TOP BRACKETS FOR LOWERED SUSPENSION C-AJJ3359 from MiniSpares.
For the rear, I set the car at the desired ride height with the HiLo's and then measured the up and down measurements with the car jacked up and the wheel removed so as to not let the HiLo drop out of the cone on full droop. The shock absorbers themselves are for the rear of my lowered 1977 Mini Clubman , and their dimensions need to be 14.5 inches fully extended and 10.0 inches fully closed ( measured from centre of lower mount eye to the top of the lower rubber fitted on the shock top shaft.)
I then got Gaz shocks to make a pair of adjustables to these dimensions. They work a treat.