Few here would likely have experience w/ the swap that you have inquired about.
1) most of the conversions here seem to center around the smaller impreza engine bay,
2) we don't have legacy b-4's here, our legacies are NA and of different wiring.
I've only heard of one case where someone put an svx engine into a usdm legacy, I believe it was abandoned later. Others have asked about the possiblility though. If you search you may find a blurb about it.
You may want to try on the UK boards as they'd be more likely to get a b4 than we would.