The original factory wiring is very complicated due to fact that uses very small tone caps that cost maybe 5 cents each and are attached on tone pots, versus caps connected between volume and tone pots. Original factory volume & tone pots are 500 kOhm. Original neck PU 490R is aprox 8 KOhms and bridge PU 498T is 14 KOhms.
I replaced neck PU with DiMarzio PAF Pro 4 conductor PU 7,8 KOhms
having the same south magnetic polarity as GIBSON 490R. I wired
it using push-pull pot as per schemantic from Smith's photo in order to get coil split and humbucking sounds. Each coil can be a single coil and mixed with hummbuckig sound.
Only drawback is that you cannot turn down volume on this neck PU however, you can easily switch to middle position turning down completely volume of bridge PU.
I put new caps 1 Ruby .22mF on neck PU and one .47 mF on the bridge tone pot.However I wil replace them with Russian PIO Capacitor K40Y-9 Series 200V 0.22~1uf . This mod gives ES-175 humbucking sound, ES-335 and LP humbucking sound and close to ES-175 single coil sounds.
This modification turns this nice guitar into really multiple sounds fusion guitar.