I fully believe a big part of Ric tone is pickup location, in addition to pickup design. Many moderate wind single coils will get close to the High Gain tone, but they do have to be located at the 24th and 36th fret area to get that harmonic node/tonality that is so signature. I have no experience with the Bison, but do have it with the T40 and actual Ric 4001/3. The T40 (in single coil mode) has it's pickups shifted a 1/2-3/4" towards the bridge vs a Ric. I measured out my friend's 74 4001 (as well as an 82 T-40) and adjusted the numbers to 34" scale to get these specs. This, in part, explains the brighter tonality of the T40. It's pickups are close to Ric positions, closer than most other basses, which mostly place pickups based on P, J or Stingray sweet spots.
This is purely speculation on my part, but a fellow TBer is acting on it and will have results soon. The Peavey Patriot has a single Super Ferrite-a moderately wound, aggressively toned single coil (much like the High Gain) located pretty much right where the Ric bridge PU is located-it's just 1/4" more towards the neck. The theory is that putting another Super Ferrite at the 24th fret location and a 3 way switch should result in a pretty good facsimile. We will see...
When I find an appropriate Patriot, I'm going to do this, too. Real Rics are priced higher than I care to spend, Chickenbakers, too, for that matter, once you account for some parts and electronic upgrades, proper fret and nut work, too. Patriots are really cool, inexpensive basses, and I love 80s Peaveys. I do enjoy a project, too.