None of my imports had an LSD, but I've a feeling my Da's old one did
Also, the muffler from the B5ZE fits fine on the V6. Lori on the UK forums fit one from a breaker AZ-3 onto his, so I'd be dubious about there being a version for each.
They have different part numbers. the only difference is the pipe diameter. the 1.5L version is 1.6" in diameter and the GS version is 1.83". IMO I would find a GS version to put onto an RS