All,
I am in the process of fitting a M3 Bumper Lip on my 1997 318ti with the standard bumper. I have seen this done before and it looks great. It does however require a bit of Dremel work to make it fit. You have to re-contour the sides of the Lip a bit for the Non-M bumper. but it does work.
I am going to noodle this for a while to come up with a step by step write up. Looking at the articles for how the lip mounts to the M3 Bumper you can use the same fastners and screws as you have to drill out the mounting holes. Hopefully I can make it look / use all the factory hardware.
It should come out schweet! It will look great when I get my 318ti lowered on H&R springs.
~Mike R~