1st and 2nd Gen single stack grips interchange as well as 1st and 2nd Gen double stack grips. Single and double stack do not interchange. (39 will not fit 59, 39 will fit 639, not 659 etc.)
Some were Ambi cut, some were not if that is important. Some look different between Gen’s also if that makes a difference. (Different wood, “different” plastic, dull and glossy.)
Jim