These pickups look interesting. I don’t have a huge knowledge of filtertrons to understand how these sound different, but I love the concept of resurrecting obscure pickups important in the history of guitar.
If I wanted info on Gretsch stuff I’d contact Tavo Vega Garcia. He seems to be the guy most in tune with that sound. I need to contact him about which of his pedals interact well with P-90s. So far I just have the Jr Barnyard and love it. Works great with single coils of any variety as far as I can tell.