Kelsey Hayes caliper pistons
I'm pretty sure the pistons from rockauto were not stainless. One of the Eight I ordered the chrome was peeling off right out of the box. A source for stainless would be nice as I have one more set I would like to rebuild.
I would also agree that stainless pistons and maybe even bleeding the brakes once a year to keep the mosture out of the calipers. You would not have any trouble with these calipers.