Fantastic looking Python!!! Congrats on getting it and joining the forum.
The hollow underlug was phased out in '67/'68 IIRC, and yours would be a '65ish. It will also have a completely polished muzzle face. They stopped that in '70ish. The front site was altered or replaced with a different one. The grips are definitely not original, as you already confirmed. Who cares though? You got a fantastic target gun from a great era. Just look at that blue finish.