Be careful which Hipshot direct replacement you get, I've tried two and neither one fits my 1967 EB0.
There are some good threads here on the electronics mods that were done to Phil's, much of it over my head electronically. In a nutshell, there were buffers attached right to his pickups, which I think effectively turns them into a primitive type of active-style, low-impedance pickup (I think... electronics gurus please correct me if I'm wrong). I believe he had separate outputs for each pickup but other than that, little is known of what the controls were. It looks like he had the four standard gibson pots (his was an EB3 from the factory, they're identical other than the routing for the bridge pickup and extra tone/volume controls - although some years of EB0 did get smaller electronics cavities) plus pots where the tone-selector and output jack originally were. What these extra pots did is a mystery and probably changed a few times over the year or two that he played it anyway.