Rewind of 63 J bass neck PU. Is plain enamel the only valid option?

[Jim Shine]

I'm no authority on bass pickups.
I thought that the black bottoms were HFV, and the Grey bottoms were PE.

On Strats, yes. There were several pre-CBS guitars that used PE. Tele neck pickups, Jazzmasters, Jazz Basses, they all used PE from the get go.