I had a Pearly Gates in the neck position of a Les Paul for years and really liked it. I now have a Riff Raff in the neck paired with a Black Dog in the bridge of the same guitar.
As Stephen said the Pearly Gates lack bass, so worked well in the neck position. I can imagine them to sound a bit thin in the bridge though.
The Black Dog has a completely different mid range voice than the Pearly Gates does, and would definitely sound alot thicker than the Pearly Gates due to it's rather large push it has in the mids.
I think the Mules would be too smooth sounding, they're not as bright nor have the same top end bite that the PG has.
In my opinion the Riff Raff is probably the closest voicing wise, but wouldn't say that any BKP will completely nail that sound 100% (which is a good thing).
