I did this a few years ago and do not remember cutting anything on a rubber bumper. There was some mild work on the upper bracket but nothing else. This was for a three core champion. I had a set of installation instructions that I will post if I can find them.
This instruction sheet originally came from the old V8 Archie site IIRC and has written instructions as well as pictures. It is not on the new web site but I think that I may have it on one of my laptops. If so I will e-mail the instructions to you.
Nelson
[This message has been edited by hnthomps (edited 04-10-2015).]