Why dont the M6 calipers work on a 4lug?
I know about rotors that the bolt pattern is different, but whats the difference with the calipers?
Assuming your car is a BJ gen platform the spindles should be identical to the 5 lug cars including the MX6,Probe, 626 and protege.
The only differences are the hub the rotor and the bracket that holds the caliper. The caliper should be the same as any other non speed protege.
So whatever swap you are trying should work just fine as far as caliper/bracket fitment.
To get the rotor to fit you can easily drill the 4x100 pattern your self.
To do a 5 lug conversion all you need are the hubs for any 92-2002 626, 93+ mx6/probe or any 5 lug protege.
You'll need wheels ofcourse.
A rear 5 lug conversion is similar but I dont know if your car has drums or discs, all local 4 lugs are drums.
The point is all you need for a 5 lug conversion is available from a local parts store as they are all wear items.