Thanks Lanner,
As it turns out, the room around a type 3 spindle is very cramped and I hardly have any room to make some sort of adapter with enough safety margin to bolt the 964 C2 rear caliper on to...
So, I will need a radially mounted caliper after all...The Boxster rear ones are the smallest I could find, so they'll have to do.
Depending on brake balance, the C2 calipers will maybe go to the rear...
Greets,
Walter