When I removed my bumper I levered the brackets off the bumper as I couldn't use it again, that left the ends of the bolts exposed, I tried grinding them with little success so I drilled through the bolt, with great success. You need a good hard 1/4" drill and make sure you drill right in the centre of the bolt, a centre punch dent would help.
Peter
Someone crashed into me yesterday
Moderator: RichardW