Found a '66 KB earlier this year. Very cool bass! Just a tad on the darker side for me. Without changing much on it (or in it), is there anything I can do to bring out a bit more top end? Maybe changing some of the caps, or where they go? Here's the info I found online, and my phone takes crappy pictures but I think that the innards of my particular bass have been left intact: Gibson EB0 bass circuitry and wiring information >> FlyGuitars
Do you have any pics of your KB? I have one as well and it seems they don’t pop up very often. I’ve gotten some decent bitey hi-gain tones out of mine but no luck in getting the very resonant unamplified tone to translate well through the stock mudbucker. I’ve given some thought to having a second pickup installed in a more standard position and replacing the stock pickup with something a bit more modern. There’s a whole lot of routing under the guard already so it would be a fairly simple task to undertake. I’d probably have a new custom pickguard made to accommodate the new pickup & control configuration.
Assuming it's wired exactly the same as the diagram you posted, I'd remove the 0.01 capacitor; it's acting as a second "always on" tone control. Just snip it off.