FWIW...

The friend's 2004 X3 M54 engine has 155K, the factory was Bosch.
Replaced with Valeo (made in Poland), perfect fit.

Couple things:

1. Bosch and Valeo are interchangeable.

2. Don't swap Pulleys (the pulleys are NOT interchangeable), use the pulley that come with the alternator.

3. The electrical connector from the car shows only 1 pin. The Bosch alternator has 2 pins, Valeo has 1 pin. But it does not matter, it works perfectly.

4. The Valeo installation is MUCH easier, the Valeo does not have the bottom bolt tightness issue. Recall that the Bosch bottom attachment is very difficult to align simply because it is a tight fit. The Valeo just slides right in, very easy.

Check the price, if Valeo is cheaper, then use Valeo.

I successfully rebuilt my alternator on E39 so wanted to do the same thing on E53. Took it out and it's a remanufactured unit, so I don't know if it's bosch or valeo unit.
Rockauto only has 120 and 90 amp units.
Realoem has both valeo and bosch 120 units, with valeo having been discontinued. The 140amp is also listed.
I do have heated seats so ideally I'd like to use the 140 amp. Can anyone confirm that 140amp will fit without issues and is interchangeable with 120amp units?
https://i.ibb.co/f4PW0W6/Screenshot-...258-Chrome.jpg

I was told by the seller, rebuild kit for 140amp alternator

https://www.ebay.co.uk/itm/ARK134-NE...wAAOSwB0hcYv4M

And I guess this one for 120 amp
https://www.ebay.co.uk/itm/ARK114-NE...8AAOSwPOhaXJnY

The seller on ebay seemed confused