seths are gr8, fralin regular, unbucker,low-winds: I have liked all of these as well., even the p92, gr8 pu, but is basically a p90 flavor, it does however fix the mud problem if that exist, but the es 347 is ebony, so I suspect its not going to be too muddy (albeit: the orig. pu's in those were very dark.)
tonefordays.com, jon is a gr8 winder, and his prices are still very good, he can wind whatever you want, love his stuff.
even older gibson 57's are nice, I don't like the newer ones as much, they sound diff. to me....could be the wood in the gtrs now though....not sure.
I currently have early 57's in my 63 es335 (orig. pu's long raped ..) and they are as good as I have heard, but I attribute that to the gtr, it sounds very alive and woody, perfect 335 tone.
how does the gtr respond/sound unplugged ??....I usually use that cue as an indicator of the kind of pu I would mate the gtr with, and I prefer most of the vintage gtrs I have to keep basically their vintage tone.
p.s. one last thing I wanted to mention that is a very good pnt: check the pots, or have a tech check , if you can, sometimes they put the wrong pots in, which totally darkens the tone and kills the sound , they have been known to have 300k pots and less, should be 500k)
I owned a 347 and went through hell trying to get it to sound like a 335. First of all, the ebony in my experience does not yield brighter tone. It actually yields more of a wide dynamic range, where the lows and highs are both smoother. So there is good high end, but it's balanced by strong and smooth bass. Not as mid-heavy as a 335.
The guitar had 300K and, if I'm not mistaken, 100K (!!) pots. I can't remember which was volume and which was tone. But it was horrible. So the suggestion to get 500K pots in there is totally right on.
The original pickups sounded too powerful and muddy in the full-on mode, and a little too bright in the tapped mode. And I didn't really want to replace them with "non-tappable" humbuckers. I just could not get on with the guitar and I sold it.
But if you are willing, first change the pots, then try either Gibson '57 Classics or maybe a Duncan Alnico Pro II (neck) and JB (bridge). Both of those have 4 conductor wiring so you can finagle some use from the coil tap toggle. Bear in mind that the stock toggle just switches between two single wires - one for full output and one for tapped output. So re-wiring is in order.