Some additional notes from OnlyOneDR...
Tractions aids can be found for the R180 in the 720, Nismo, Quaife, Kaaz, and Cusco sell LSDs, mostly because the R180 was under the earlier Zs and newer Subarus. Not sure if you can swap the bolt retainer in from an open R180A carrier to get it to bolt into an HB or Frontier axle. I did that trick to get my 300ZX lsd into my R200A.
The HB and Frontier front axles are "A" axles, (e.g. R200A, R180A). The A designates an offset carrier. The R200/R180 are different because it is centered and does not have axle tubes on either side. (Still trying to figure out why AC lists the H190A?)