Redline MT-90 (GL4) in Gearbox, Redline 75w90 Gear Oil (GL5, not NS for our Helical LSD's) in Diff.
Both are 75w90, but the GL4 has less extreme-pressure additives and has controlled friction levels - as excess EP additives can be harmful to synchros, and excess slipperiness can hinder shifting performance. The GL5 fluid is required in the diff as it provides better lubrication and wear control, and we don't have synchros to worry about here.
I'm running the above combo and I am happy with it. There are other products that will work also but it's worth making sure the factory requirements are met. For the record, I believe the manual recommends GL4 75w90 for gearbox, and GL5 75w90 for diff - hence my suggestions.