I've got an '00 pre-facelift E39 M5, bone stock except for removing the 6-disc changer in the boot and wiring in an aux adapter.
I just bought some wheels, and we'll see if they fit! I went 285 all around, which will be tight up front (with no camber adjustment from the factory). Other than that I'm going to try to keep the modding light, although I'd love to drop in a Stage I or II S/C kit. Welllll, I'll probably do the muffler delete. It saves like 35-50 lbs, and makes it sound better. But other than that stock and just enjoy it until I'm richer.
Did you do all the work to your E46, either choosing and/or installing all the mods, or did you get it modded?