I find that the Crawler neck (which, I believe, is the same as the slightly cheaper Abraxas neck) can get you in the ballpark -- even within the bases -- of some very fine Slashy tones. Sure, the Crawler/Abraxas neck is technically hotter than Official Slash Pickups, and has a different magnet, but you can indeed get that vibe pretty well IMO. And it's just a great neck pickup anyway! :)
I imagine you could balance the Mule neck with the NB bridge -- people have been very happy with Warpig bridge, Mule neck combos as I recall! -- but my sense is that the Crawler/Abraxas neck might sit in there easier.