A straight bolt in 10 bolt B/W would be the go, they are still available you just need to keep looking. Due to them showing their age tracking down a good L.S.D 3.08 is going to be a bit harder. if you cant find a leaf spring assembly diff you might be able to track down a coil spring housing and weld on the spring pads, very easy to do. If you manage to track a late model diff from a statesman they have disc brakes. Experience has told me 10 bolt B/W are real only good enough for around 350hp before you can start to run into reliability problems. The gearset is the weakest link. Don't get me wrong they are much stronger than the smaller axle breaking bango setup but still have their limits.

Hate to say it but you might be better off with a 9" and have a wide choice of components(LSD, axles & brakes) and ratio choices.