a 3rd gen 4runner has a GVWR of 5250 # so 29" front and 30" rear bumper height are the limits...

The front bumper height of trucks whose gross vehicle weight ratings are 4,501 pounds to 7,500 pounds shall be no less than 14 inches and no more than 29 inches, and their rear bumper height shall be no less than 14 inches and no more than 30 inches.

since you're planning on a custom bumper, depending on the officer who pulls you (it will vary - trust me) - he or she will measure from the lower edge of the aftermarket bumper if it appears to be in the stock location. however, them may do this measurement...

In the absence of bumpers, and in cases where bumper heights have been lowered, height measurements under the foregoing provisions of this section shall be made to the bottom of the frame rail. However, if bumper heights have been raised, height measurements under the foregoing provisions of this section shall be made to the bottom of the main horizontal bumper bar.

so just be aware if the bumper is raised or lowered. i know with my taco and the bumper was raised for the body lift, they measured from the bumper's lower edge. when i lowered it to the stock location, they tried to measure it from the frame but i told them it was in the stock location and they measured it from there.