There is quite a bit of Clearance between the Piston and the Bore. E
he main issues are if the Pistons are pitted in the Area the Seals ride on. Are the Bores deeply pitted and there can be no pitting in the sealing area where the Big Square O-ring Seal goes.
I am meaning no pitting where the outside face of the O-ring seats.

Also if you noticed the Pistons have a cut out area that has to be positioned in a certain spot when they are installed.
On the ATE Calipers the Heat Shields give you clue on that. I have no experience with the Bendix ones so cannot comment on them.

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84 300D, 82 Volvo 244Gl Diesel