The Boxster S rotor that I mocked up and works with the early NA backing plate is pn:986.352.403. The brakes shoes end up 'just' flush with the 'drum' surface (laterally speaking). No spacers are required to centralize the caliper.
The 86T rotor is 951.352.041. You will need 3mm shims and longer bolts to centralize the caliper.
As a shameless plug
, I now offer hardened washers and longer grade 10.9 bolts for the job. About $C18.
Lanner