You can try and find the black insert for the two holes (hard to find on its own), either ebay or wrecker or you can buy an SS/SV6 bumper from ebay. They fit straight onto the Omega as well.
Or, do a dodgy and cut a hole in your black insert till you find a genuine one.
Holmart have all you need. If you buy the exhaust through them, you just ask for the parts required. Cost me $138 for the insert, double diff exhaust hanger, left rear muffler hanger, and some rubber mounts, and the black insert.
is this what i wil need 1) 1 Rubber Exhaust Mounts $11.00 1 Rear Exhaust bracket. $20.00 1 Left Hand heat shield 1 Diff double exhaust hanger SSV Lower bar inset! (For twin exhaust type