The Bendix rear calipers are shared with the original Lotus Esprit and Renault Alpine A110 Group 4 cars. As it was an upgrade for Alpine it must have had some cache! Might also have been used on the Renault R30 V6 but I've not been able to confirm that.
There's nothing wrong with the calipers, they are just hard to service.
A recent innovation is grooved and drilled front discs for the Murena. As the Murena suffers from front brakes overheating this should be a worthwhile mod.
Original brake pads have become quite hard to obtain but Green Stuff produce the Murena brake pads. I think they are quite hard but at least they don't cover the hard-to-cleam Murena alloys in black dust.