I have Thule cross bars installed on my sedan. They utilize the threaded holes underneath the panels in the roof. Makes installation and removal very easy! If you buy a used Thule rack, make sure it comes with the rubber washers (1 per bolt) and hex security wrench. After that, all you need is a bike tray. I have a Rocky Mounts tray and it fits just fine.

The one speed bump during installation was having to chase the threads in the roof of the car. This step was not explained or even mentioned in the installation Thule instructions. There was just enough paint in there to prevent the hex bolts from threading in cleanly. Took 5 minutes to carefully chase the threads and all is well. Also make sure to double check your measurements when tightening the feet to either end of the cross bars. Gotta be even!

 

Check measurements if the bar is even on both ends? How precisely does it need to be even?

Are you talking about paint in the Thule bars? I could make sure that's not an easy at time of purchase.

 

Thule 753 is the one you should look for.
Thats the only thule cross bar foots that are designed for E46 and E39s.

Else, OEM profile 2000 racks.
You need to protect the paint on the slots, forgot the part number, but you need 8 plastic pieces with adhesive on the reverse. I made my own.
The holes on our cars take M6x16 1mm pitch screws. So, you can get the screws from local hardware store or thule or ECS or BMW.
Get 4 washers, and 4 rubber washers.

I have OEM cross bars with thule fork mount.
I will write up a DIY soon on how to mount thule bike racks on the OEM cross bars.

I got a good deal on both, so after spending a week by trying various adapters from rackattack store, I was able to fit thule fork mount bike rack on OEM roof rack without any modifications.

 

I have OEM cross bars with thule fork mount.
I will write up a DIY soon on how to mount thule bike racks on the OEM cross bars

pictures in that other thread you started will be helpful. I need to do the same thing and I appreciate the research you have done to get to this point.

 

As promised, here you go guys. A DIY of how to install thule bike rack on OEM roof racks. Part numbers too.

http://forum.e46fanatics.com/showthread.php?p=15640816#post15640816