The final result was one of the best guitars I've ever owned. The Filter'Trons were mounted to wood pieces that were then mounted to Gretsch English style bezels. I didn't install a tone switch, but instead replaced the tone knob with a 4-way rotary switch; with setting 1 having no tone cap, setting 2 having the lighter newer style Gretsch tone cap, 3 having the heavier newer style Gretsch tone cap, and setting for having the much muddier lighter vintage Gretsch tone cap. The caps came from TV Jones. The volume pots were unchanged after all.
The end result was a Gretsch 5120 that sounded very much like a 6120. Going from the stock Gretsch-buckers to Filter'trons added so much more clarity to the sound, I equated it to taking 3 sleeping bags off the amp. I definitely was achieving that "Gretsch sound".
The final mod I was going to make to this guitar was pinning the bridge. I had all the materials to do it, but due to an unexpected divorce, ended up selling most of my guitar/bass gear, including this 5120.
Gretsch now offers the 5420 (5120's are discontinued). This guitar offers blackout Filter'Trons stock, binding on the F-holes, and hump-style inlays. The crappy stock tuners are still there for replacing; thinking the Grover locking tuners might be a better, less invasive option. These also have a tone knob like the 5120.
