Hi riffpowers,
Early Korina Hamer = yummie indeed :D
I have BKP-rewound P90s in my Epiphone Casino, the bridge P90 similar to a BKP91. I think the BKP91 would be well suited for your purposes. It has enough poke/sting to sound raw with your Matamps without going muddy. This is helped by the clear and defined attack on the wound strings, which is very much like the really old P90s. Personally I wouldn't use a higher output PU because this will increase risk of muddiness and lessen dynamic response.
Also I'd like to add that a level booster like an MXR micro-amp or any other make really works great with this particular PU. I much prefer the amp-going-wild sound of a booster to any overdrive pedal. Your Matamps are also well suited to this approach.
Good luck,
Martijn