Assuming the track car would only be driven on the track and to and from it, and the DD would be used for weekend drives, I'd break it down like:
- DD: 356 Cold in the winter? Screw it!
- Track: 993 Turbo
- Burn 959
I'd rather burn the 959 than track and maintain it. The 993 Turbo is essentially a 959 minus the exclusivity anyway.