Ben,

I have a brand new Porsche Junior Plus car seat (never used). I have it up on craigslist and here is the ad.
Porsche child seat, 33 - 80 lbs, part no.955 044 801 03 , brand new never installed, was meant for the back seat of my 996, you can mount in the front or back seats David 201-400-4408 cell

Ben, yes it will fit in a 996. (it will fit all 911 from 1999 on). In fact the manufacture date of the seat in 2003, so it was probably made for it ))