I'm leaning towards Riff Raffs as well.
I've not tried my Mules in my Explorer, they might be rather tasty, but I like them where they are in a Les Paul type guitar.
When I got my Explorer, I was after making it into my "blues-machine". But I also wanted it to do blues-rock and "classic-rock". My reference points were things like Allen Collins in Lynyrd Skynyrd and late 70s rock tones just before it started getting called "metal".
My understanding is that the Riff Raffs are the BKP offering most like the type of humbuckers that would have been in many of those guitars (including a 76 Explorer!), and I had a set, so I put them in and loved it. It was 60s-70s rock incarnate :lol:
I've since swapped things around further, and my Explorer has had Mississippi Queens for nearly two years now. It was just an experiment, but it worked well for me. I'm treating the MQs more like humbuckers than singles. I'm really a single coil player, strat mainly, and the combination of Explorer and MQ is perfect for me - I know they're not humbuckers, but they do what I want from HB territory, and they respond more like I'm used to. It might be worth you looking into that sort of idea if you're really a single coil guy most of the time.
But if you're more of a humbucker purist (and I think I would be in an original 76 Explorer! :lol:) Riff Raffs is what I'd suggest.
And welcome to the forum! :D