Whenever I’ve checked sigs website about things like that, they’ve never said that they couldn’t be installed on German made sigs, so my assumption would be that old/new or German/American wouldn’t matter.
The designs are the same, it’s just material and point of manufacture are different.
But I’d contact either sig sauer or Bruce gray for confirmation, wait in fact I’d contact Bruce gray (gray guns), he probably knows more about sig pistols than Phil Strader!