Rearend maintenace

[solve4x]

or should I say first attempt at rearend maintenance in 27 years.
87 R10 305 2wd
What type of gear oil and how much?
I assume I need to remove the backplate to drain? 
The Haynes answer to all of these questions was "it depends".
Hopefully I can get the fill plug out...it looks stuck as can be.
Any other suggestions appreciated.
Scott

[NCali]

I would get two quarts of 90 wt. You will use about 1 1/2 . Fill it until oil runs out of the fill hole

[bake74]

     If you have never opened it up before, I would, then clean it really well put on new gasket and fresh oil.  This way you can inspect the gears for wear and to see if anything does not look right.

[Captkaos]

I would pull the cover and inspect everything, clean any junk out check the gears and then replace the cover pull the fill plug out of the side and fill it til it to the bottom of the fill hole.

[solve4x]

All done...gears looked great.
It took 2.5 quarts of gear oil, full to the fill hole level.
Is that a clue as to which rearend it is? .... 10 bolts, fairly round gasket.
There was no tag present.

There were several gasket choices at the parts store, so must have been several different rearends in 87.

[Captkaos]

There was only 1 rearend for 87 1/2T trucks.  a 10bolt.

[solve4x]

okay...good to know!!