I had the same problem with my Explorer when settling on a st of pickups for it - all too bassy. This won't help you, but I couldn't find a set of pickups that worked in mine and ended up with EMGs.
For the most drastic change in tone, I'd try these in the following order...
* change to 500k pots (if they're 300k). If they're already 500k, get 1M - can always put a resistor across the pot to bring it down to 750k for less brightness.
* disconnect the tone pot completely
* aluminium tailpiece
I'd use the old 50s Gibson style pickup wiring anyway as it sounds subjectively better to my ears - louder, crisp and more open like a blanket has been removed from over your tone.