Not sure bolting it to the pan is a good idea, too much of a chance for a leak, or a stress crack around the hole . If you hit something all of the pressure of the impact will have to be absorbed by the very small bearing surface of the pan. Were it me, I would find out how the plate is attached to the old pan, remove it and transfer it to the new pan. If you have it welded on you can reinforce the welded area on the inside and spread any impact stress out over a much greater surface, should be able to make it better than new. Just IMHO.