I don't know. I think OSHA, the EPA, and whatever bunch makes them put skulls on the back of Lysol jugs would have had fits if Rick let it be known they were putting blobs of lead in the bass neck. Or heating it up in the factory to begin with. Lead is great for shooting through deer hearts, EB-0 necks, and old Detroit valve seats, but bad for just about everything else.
I had an early 70s Rick 4001 and it was dead in general, especially in the middle of the neck on the D string. Octaves up didn't ring out. I played plenty that weren't dead though.