Not wanting to drill holes in the face of my bumper and having an old plate bracket from my TR6, before I added the late model chrome frame, I drilled a few holes and found a nice fitting unit. Easy enough to take on and off when I want to.
I drilled 5/16" holes and tapped the inner bumper frame with 3/8" X 16 threads. Some 3/8" stainless bolts and I did use extra flat washers between the bracket and the bumper to bring it down a bit lower, which keeps it level with the top of the bumper edge. There were two bolts that hold the bumper fascia in place and with the washers, the frame is a hair below them, so no interference there.
-By Paul Rego