Well, what I'd LIKE to put on my bass is a GENUINE RIC "Vintage Treble Pickup Assembly" (
http://www.rickenbacker.com/pdf/bpickups.pdf), but I have been informed by RIC that, "the treble pickup for the 4001v63 bass is not currently available as an accessory."
So, if RIC doesn't make what I want available to me, then I'll have to find another source; whether I make it myself, or a list member makes it, or if it's manufactured commercially.
Know this: (Since I started this thread) I would rather buy ALL parts from RIC.