I wanted to do this to my 1995 945 so I went to a junk yard to see how sun roofs were put together. I suggest you do the same. There appears to be a major difference in the roof structure. in a non-sunroof car, there is a stiffing beam that extends across the roof of the car at or near the ceiling light. The beam did not exist in a sunroof cars I looked at. Also, you will need to cut out a section of the roof of the donor car to get the sunroof mounting bracket. you would then have to have this welded into your car (and have a new paint job). It appeared to be a major undertaking (and probably cost a min of 500.00). Did not appear to be worth it at this time.