Thanks for the advice, hardluk1. I did, indeed, buy the service pack from Wolff. The 659 is in great shape, but is 30+ years old, so I'm gradually going to accumulate a supply of spare parts "just in case". Also bought a new barrel bushing for it.
One further recoil spring question: will the factory standard spring be ok for both 115 gr. and 147 gr. ammo (both non+p)?