It's odder than I thought.
68-SS X3-M 130mm overall races about 48mm apart 68-SS 114mm 48mm 70-SP 108mm 54mm 70-SPc 110mm 52mm
The first one is hollow, too, with a bulge in the center and a hole like an oil hole. The two Italian ones do have their races slightly different.
Is there, perhaps, some thick/thin cup stuff going on here, too?
David Bean
Arlington, MA