To follow up on what Big Daddy said, Sheet metal aftermarket quality varies a lot, its usually best to stick with factory components. Many electrical components for BMW are made for BMW by Bosch and whether the label says BMW or Bosch they are likely the same. The same goes for ATE and Siemens, both are suppliers to BMW. When it comes to upholstery, when I redid my 1989 325i I went to a local shop and saved a bundle and got a great custom job. If you want, the local shop can even purchase fabric etc from BMW. The key is to try to do homework before buying and ask somone before you buy if you are unsure. If you are a BMW CCA member there is a lot of knowledge available for the asking. Just call one of the technical advisors to the club, its free.