i have the same dillema. Except I have a full high mount M4(not just pipes) for an 03 while I have an 05. I called M4 a few times. Either I leave a message on their voice mail or I tell a person that actually answer the phone. They take my info and say someone will call me back and nothing.
Anyway, when I get to doing it(waiting for someone to help since my arm is fuct) I deal with it then. I figure the pipe will wind up being too high for any brackets since the 05 is lower than the 03. After installation, I'll see whats going on and most likely hit up an auto supply. There I'll see what they have so I can just attach it to whatever part of the bike makes sense.
I don't mind having the pipe at a steeper angle or the pipe coming up higher than it's supposed to. Nope, I don't plan on having passengers.