Hi James,
All of my remaining 17 brain cells agreed that they have never seen the new-style Mahle pistons in a JD specific K532 that had not otherwise been rebuilt with a new piston. Indeed, the Kohler parts manual does not show Mahle pistons being used in any K532. Mahle K301 (Magnum 12) pistons should work as replacements in the K532. As you know, new-style Mahle pistons were used in most K582 engines, although the Kohler full-skirted pistons were used in some.
Harold