As for the part numbers, there are two ways. The one I used in this case was that I have an old (1964) parts price list. Simply look up the old and any changes will be listed. Secod ay is to pad the old number with zeros to make it a six or seven digit number. For example, your 41-123 becomes 041123 or 0041123. Look for that number in a new parts book and it will show the price or superseded number (if it hasn’t gotten lost in history).
The end of the packing nuts and bottom of the threaded holes is tapered. That squishes the packings against the rotating needle. Not necessary, but an improvement, some newer motors added thin nylon washers at the ends of the packing stacks to make them more durable.
