Small update:
Most of the engine work has been completed.
The bad news, the Thrust Bearing isn't looking to the the cause of the bearing whine issue, it's possibly the input Shaft Bearing. However when they tried to split the gearbox, they couldn't as the 5th gear hub (so they say) is seized. Bummer. Will probably chuck a second hand box in there and call it a day. I'd love a LSD box, but they're too rare here in NZ to find, so I'll have to do without, which is alright.