I got the 554C wiring reconfigured without any trouble.
Unless there are wiring variations necessary for the 46B coil that I am not aware of, the 554C produced more sidetone to an annoying level, and reception quality was degraded. I have a feeling that additional wiring tweaks could be required. One thing I noticed was that the typical click could be heard in the receiver when the handset was lifted off the hook, but when the switch hook was depressed, there was no click. Even the 634 provides a click both when handset is lifted and when hook is depressed.
So, I hooked the handset and stand up to the 634/101 coil again and the improved service I had been enjoying was restored, with sidetone reduced to an acceptable level and reception much more clear. I think I'll leave it at that. I want to use the phone more, so if the 634/101 subset provides the best possible performance, that's what I'll stick with.
I'm going to order a 557 receiver element from Steve Hilsz anyway. Mine has bad threads that are chewing up the bakelite spacer, so I'm also getting a spacer from him. We'll see if a different element changes anything. I doubt it, as the element currently in my phone looks almost brand new -- except for those bad threads.
