Another low cost solution to consider is using air shocks.. I've used them for years with relatively little problem..

Even with the extra weight I've added, (rock sliders, rear skid plating, rear dual battery and tool box) the air shocks have provided acceptable lift (I run 95psi in the shocks) to not only overcome the spring sag, but bring the rear height back above original ride height. The shock mounts on the 4Runner are massive and beefy enough to carry weight full time.

I've used both the Gabriels and Monroe air shocks and prefer the Monroes.

The Monroe shock you can use on the 4Runner is the part number MA700..

Anyone know if they make a model that would fit 84-88 Trucks and 84-89 4Runners in the rear?

My Truck: 1987 XtraCab DLX 22R 4WD 5 Speed Manual
"Speed has never killed anyone. Suddenly becoming stationary, that's what gets you." -Jeremy Clarkson