Mark replied:

I had the same problem with my GQ, considered polyairs but heard stories of damaged mounts so went for springs instead. Priced the big suppliers but ended up going for King springs at a big saving. I am told that TJM springs are King Springs. So far I'm very happy with the results.

Andrew replied:

I had the same problem and decided on Polyair. Air bags can be addjusted to different weights and they have one year warrenty. If you put heavy duty springs you may end up with very stiff back suspension when unloaded.

CLIVEB replied:

Enforcer springs are the most economical,these are in fact king springs.
scratch of the blue paint and you will find king yellow.
Also the selection charts used by enforcer outlets is put out by king springs.
I have used these on 3 nissans with no problems,trips include the simpson,canning and most recently arnhem land.
Get progressive rate springs and you have the best of both worlds.

CLIVEB replied:

FITTING IS RELATIVELY EASY.BE SURE TO USE SAFETY STANDS AND BE AWARE OF THE STORED ENERGY IN THE COMPRESSED SPRINGS.VEHICLE WHEELS MUST BE SECURELY CHOCKED.REMOVE THE ANTI SWAY BAR BOLTS AND THE LOWER SHOCKERS.THEN YOU NEED TWO JACKS,ONE TO RAISE THE BODY AND THE OTHER THE AXLE. REMOVE THE WHEEL LEAVING THE JACK UNDER THE AXLE.JACK UP THE BODY UNTIL THE SPRING IS ALMOST FULLY EXTENDED,THEN LOWER THE AXLE JACK UNTIL THE SPRING CAN BE REMOVED,TAKE GREAT CARE NOT TO STRETCH THE BRAKE HOSE DURING THIS OPERATION.
REFIT THE NEW SPRING AND REVERSE THE ABOVE METHOD.
THE FRONT SPRINGS ARE HARDER TO FIT WITHOUT DAMAGING THE BRAKE HOSES,USUALLY REQUIRING THE RADIUS ARMS TO PUSHED DOWNWARDS. A SPRING COMPRESSOR ALLOWS THIS OPERATION TO BE PERFORMED EASILY (YOU CAN PERHAPS HIRE THIS EQUIP OR PURCHASE FROM ACCESS SHOP) TAKE CARE AND GOOD LUCK.