Diff oil and transfer case Oil

Just got my 1993 3.0 4x4 with 140k miles automatic transmission
Need to change the oil
Please correct me before I do the oil change this Sunday

1.Diff oil AW 80-90 API GL—5
Does this mean gear oil? I do have stop tech gear oil laying around in my garage. Can I use the oil?
How many quarts for the front and the rear? Do I fill up until the oil drips from the filler hole?
2. Transfer case use dextron II ATF. how many quarts? Or stop as the filler hole starts to drips
I do have the redline MTL gear oil, can I use it for the diff?

 

The supertech 80w90 is fine for your diffs. You will need about 4.5 qts total. Fill until it runs out.
Transfer case is less than a quart. From what I have read, you should be fine with the Dex6.

 

Dex VI is damn spendy to put in a t-case but should work. A common Dex/Merc (which will be Dex III) is more common and affordable, but if you've already got the VI neither availability or cost are factors.

I personally believe you'd be fine with Merc V in a t-case, although FTM (Ford Tech Makuloco) has a video about how it'll make t-cases explode. HOWEVER, he was speaking of Ford AWD 'cases which have clutch packs and engage automatically. A basic, manual t-case effectively just needs a lightweight oil, which ATF is.

I wouldn't use MT fluid in a differential.