Porsche boxster 16" wheel fitment (1303)

[MdR]

I think it will be the 944 aluminium arms that dictate what wings you'll need. I reckon you will need wider ones.
You can work out the extra track of the A arms over a standard car then minus the gain by the bigger offset rims.
Or you can simply measure across the outer faces of the 2 rear rims & compare to a standard width car.

[volksartist]

For interest sake, I have a ghia with stock irs rear and the 7 et40 with 205-50-16 fits with no trouble (Drums). Front 6" et50 fits fine with 195-50-16 but was not clearing the swaybar clamps. Need an over the arm style sway bar. Speedo dust cap is a bit of a pain too. It sticks out and gets in the way of the center cap. (stock ghia rotors)

Kevin