Nice find!
I've never been thrilled with the #3 wood screws used to mount Thunderbird pickups.
I have been thinking about a better way, and here is what I've come up with.
Using a 4-40 machine screw and an EZ Lok steel insert stability, adjustability, and longevity are all improved.
The insert is set into the wood using a screw and washer so it sits flush at the surface.
During installation, I use a washer at each end of the spring, so none of the compression force is pushing the insert's threads out of the wood.
All of the pressure is applied to the internal steel threads and the back of the pickup.
Surgical tubing allows the "spring" to be custom-sized for the application.