I have never ordered a replacement audio loom but I imagine that you do so by using your VIN number. So if you used yours you would have an exact replica of what you already have.
If you were feeling lucky you could find another car of the same vintage that has the right specification (whatever that might mean), take the VIN number and order against that. But if it wasn't right for you or didn't work I don't imagine BMW would be too helpful.
And then you will need a working MOST bus in your left-hand trunk area (and something to control it) as well, since the standard Hi-Fi amplifier uses K-Can.
As has already suggested, it would be a lot easier to use non-BMW components, especially as you don't have MOST now, so don't have to worry about it.
There is a very useful training document published by BMW in 10/06 called "E70 Audio Systems" that described the differences between Hi-Fi (standard audio) and Top Hi-Fi (Premium Audio). You should search for it.