I've just measured the HRWs in my H535, and the neck is 7.3k while the bridge is 8k. I don't know what magnets were used (does anybody?), but I believe the Schallers, on which the HRWs were based, used Alnico 5 magnets. I also just checked a pair if Schallers (taken from an H150 a while ago) and they are neck - 7.7k, bridge - 8.3k.
While I have the multimeter out... Burstbucker 1 - 7.7k, Burstbucker 2 - 8.2k, Seth Lover neck - 7.3k, Seth Lover bridge - 8k (these are both Alnico 2).
According to the SD site, the 59s are neck- 7.6k, bridge 8.2k (similar to the Schallers). Looking at the Bare Knuckle site, the Riff Raff humbuckers are Alnico 5, neck - 7.4k, bridge - 8.2k. I'm sure if you contact BK they'll be able to advise you on the options. There are also a fair number of winders in the UK who will make a custom pickups - Radioshop, Creamery, Oil City, Catswhisker etc.