The Firebird humbuckers are very bright and do not have a lot of output. The closest BKP humbuckers therefore should be in the Vintage category, and there the brighter ones like the Stormy Monday or the Riff Raff. This is only by description of course since I have not played the Vintage BKPs yet. I do have a set of Lollar Firebirds though.
Cheers Stephan