If you can't tell whether it's bright or dark, it might very well be 'balanced' :) I'm not that familiar with Les Paul's from that era, but supposedly they are with ebony boards? Maple or mahogany top?
Anyway, what tells a lot is what you don't like about the current pickups. EMG 85 is a pretty common pickup, and what it sounds like in your guitar is the key here. You said it sounds bright/thin, so your guitar is probably a bit on the brighter side of LPs. The ebony (?) board might contribute to that too and should be taken into account.
But the more important question: what kind of a tone would you like to get from the guitar? There are a number of pickups that could work very well there. Tone references, like songs work well on that matter 8)
-Zaned