Although no one has vouched for them I still think the Abraxas is an option. I do really enjoy a bridge pickup that has a bit more push than vintage voiced pickups but I love the original, PAF sound for the neck, which to me by the BKP description is the Abraxas. I also don't tune terribly low (D standard) on this guitar so having a ridiculously tight bridge pup isn't paramount, especially with the amp I'm using; I play through a 1981 Marshall JCM 800 2203.
I'm also very interested in trying the Alnico IV route. I have played Mules in a friend's PRS Spruce Hollowbody and I love the frequency balance, clarity and overall vibe, I just need a little more balls behind them, especially in the bridge.
I'm pretty sure a mule in a les paul has a lot more balls than in a PRS, specially the latter being a hollowbody
also, having it closer to strings makes it considerably meaty in a les paul, although it's not a FAT sounding pickup like a dimarzio 36th anniversary or black dog
honestly, after having tried a lot of bkp models and other brands, the mule was probably the bridge pup that surprised me the most
the level of detail and "juiciness" on the clean, crunch and mid gain sounds is absolutely amazing
the A4 seems to subtly melt the notes together in a very organic way, so it makes things creamy and thick but you still can hear the note separation
I'm not sure the abraxas can keep that sort of clarity, being hotter wound, but being a BKP, it can't be less than great
the vhII is hotter, but it's more noticeable in the picking attack, than actual sustain
it has a harder and edgier sound than the mule, you can tell where it comes from
the black dog is a much middier pup and a bit less open sounding in comparison, which delivers a more modern feel, like there's a wall of mids on chords and that half-c--ked crybaby effect on leads
it has a more imposing sound, rather than the transparency of the other mentioned models
you have a nice rig, by the way
that white '89 is really really rare
I know a guy that owns one just like yours, but I think it's the only one in my country
if you're pushing the JCM with any sort of boosting device, you won't miss anything from the mule