Looking good. The foam board is a great idea.
I can't remember how the 4Runner frame compares to a pickup, but if possible I would suggest adding a couple mount points to the underside of the frame. They will help prevent the bumper from slipping on the mounting bolts and pushing up in to the body.
Something like this:
I learned the hard way with the last rear bumper. Damaged my tailgate. Ill be welding this one to frame
