I was pretty set on using an easier method but ended up removing the front bumper and using a dremel. On the backside of the bumper the spots to cut are already marked so that makes it pretty easy. I used a drill bit first and just drilled a hole on the top and bottom of each spot so I just had to dremel two straight cuts down each side. It was a much easier project than I had anticipated.
This was the way I had originally planned to do it but I just figured cutting the clips off of the backside of the valance was just as much work:
5th Gen 4Runner - Front Bumper Valance Swap from Off-Road to SR5