Re: Improving LP Deluxe
I have a '76 Deluxe as well. Mine was made in Nashville, and yours likely was, as well. The original pots in mine all measured around 350K. A switch to 500K will brighten the guitar up a little bit. I can't guarantee that it will get rid of the "murk," though. This could be attributable to your cable, amp settings, the condition of your tubes, yadda yadda yadda. FWIW, I had mine routed for full-size humbuckers, and the Seth Lovers I have in it are great with my amps.
As Lew said, the microphonic feedback you're experiencing has nothing to do with the pots. Those mini humbuckers are very prone to do that. The minis in my Lester squealed like crazy.