does anyone know the biggest tire u can fit on a 1990 4runner with stock suspension and a 3" body lift maby a 3.5" if I need it.

Definitely, 32's...maybe 33's. BF Goodrich makes 33x12.50R15, 33x10.50R15 and 33X9.50R15 in case you have trouble with clearing the front while turning. 33X10.50's might be a good choice especially if you have stock rims.

From the 4Runner FAQ thread:

"What is the largest tire I can fit under my stock 4Runner?

For 1st and 2nd gen 4Runners and trucks you can safely fit 32x11.5s with little or no rubbing. For 3rd gens you can fit 265/75 R16.

However, tire size varies by manufacturer so some may rub a little more than others. Mud tires tend to vary more than street or A/T tires so they may rub even more. Also, 2 hidden concerns with going bigger are the speedometer offset and the possible loss in power. The loss in power is the result of the change in the effective gearing by going to a bigger tire. The severity of the power loss is dependant on your present gearing and how large a tire you moved up to. To remedy the loss of power you should change your gears in your differential(s).

Having said that, usually if the tires are only enlarged 1 inch most people just live with the loss of power and speedometer error. Most 3rd gens don't feel the loss of power because the engine is more powerful."