best calipers to use are the MSF/MSP/euro spec BJ/Capella (or Euro 626) diesel wagon rear calipers
they use larger pads than what the (regular) 6 uses, and uses the same rear pads as the FD RX-7, so wide selection to choose from
they bolt right in, and no need to do anything to the parking brake cables!
the discs are 280mm, so the mazda6 ones might fit if you have 5 stud, or you can simply get the correct ones from those cars I mentioned.... for 4 stud, those MX-5 discs might work as there's only 4mm difference... the pads probably will sit right on the edge instead