It likely has a 500k pot in it. that should be fine, but if it's a 250k a 500k might help. My epi tbird had a .068 cap in it (maybe yours too?) and when I went with flats is was too muddy. I put a .047 PIO cap in and it brightened up nicely, especially through my Ampeg! Growly as all git out.
It's trial and error, just keep dropping cap values till you get what you like but they don't call those mudbuckers for no reason! String choice will help too, something like Rotosound Swingbass 66 stainless are very bright, piano tone. Any stainless will be brightest but hard on frets.
for more on caps see this thread I posted and the answers I got. helpful.
Tone Quest, PIO caps & Pots,