What oils?

[Ted]

I'll be doing a full service tomorrow and want to make sure I do it right, I'll be replacing the engine oil and filter, the fuel filter, all diff oils and manual transmission oils and the transfer case.
After having done some reading, and been to supercheap auto I ended up buying a load of oils, but at the moment im not sure if I've done the right thing.
For the engine oil:
At the shop they recommended 10w-40, however after some digging I found a Gregory's manual and they claim 20w-40.
As for the Diffs, transfer case and manual transmission I've bought Castrol VMX-M 75w/85, and again Gregory's claim to use 75w/90 GL4 for the manual transmission and transfer case (which isnt much different really, or is it?) however for the front and rear diffs they claim 80w/90 GL5
My question is what do you use?

So far I've bought 10 liters (2x 5L) of Castrol 10w/40 magnat
4 liters of Castrol VMX-M 75w/85
1x Oil filter Ryco Z170
1x fuel filter Ryco Z322 (still on backorder)
And for those paying attention yes I'm still about 8/9 liters short to do the front and rear diff (80w/90 GL5 according to Gregory's)
Obviously I'll be going back to pick up the fuel filter which wasn't in stock but I may as well get it all right the second time I go there, or third time's a charm they say...

My patrol is a 1990 GQ DX with the 4.2 straight 6 manual (TB42S?)

Cheers,

Ted