dont botther trying to find ma61 stuff.. i tried looking and their isnt much around.
just get a coilover sleve kit from gilly or dimitri.
for the rear commodore shocks are shorter. might be able to find a AGX model but not sure. with the springs its hard since its a heavy car to start with so not many cars are going to be stiffer. the rear sping diameter is slightly bigger than ae86/ke70 and you could run the springs from one of these. but they need to be stiffer (7-8kg) and longer. not sure on exact lenght but my 200mm 6kg springs absolutly slammed my cressy haa
hope that helped mate