David,
I'm in Central Illinois. 1986 Plus* Vitesse.
I use Red Line 75w-90 Gear oil. It already has the friction modifiers for a limited slip Diff. I buy from Pegasus Racing in Wisconsin.
https://www.pegasusautoracing.com/The drain plug is under the 'pumpkin'. The filler is on the rear of the Differential, a bit lower than half way down. PITA refilling, you'll need a funnel and hose. The fuel tank will be in your way.
The filler nut is a square headed pipe plug. Fill the case until it just starts to weep. I use a non-curing thread sealant on the plug. I use Hylomar Blue. Do NOT over tighten, it is a tapered pipe thread and you can booger things up...
If you have the LT-77 or R-380 tranny, the Red Line MTL works nicely.
Ron Davis
