I have used a pump adapter for a gallon jug and pumped oil into the fill hole till oil just reaches the bottom of the fill hole.
I have also added a piece of tubing onto one of those long tapered plastic funnels and fitted the other end of the tubing with an elbow fitting. Easy then to snake the elbow ended tube from the engine compartment down along the side of the trans and stick elbow into fill hole. Add oil.
A spread of newspaper and the drain pan underneath, just in case.
It's been said many times, but bears repeating: Make sure you can remove the fill plug before you start draining any fluid. We've had BB members who have drained their tranny before realizing they couldn't get the fill plug out (sometimes just due to lack of the right tool).
you can if you want it easyer, to fill the diff. by pulling the spare tire out it's wheel well, removing the forward rubber plug and running a plastic tube from there.. put the oil in a hot bath for 1/2 hour this will make it pour easyer.. a hint.. you will need 2 bottles of trans oil for the rear end.. on the first bottle take the cap off. snip off the nipple to fit the plastic tube....EPOXY this tube to the nipple, ket set.. this way the plastic won't slip off as you invert the trans oil bottle.. i had some problem with this , untill i epoxyed the plastic tube to the nipple..
If your spider is 84 and need to find out if it has LSD differential check above the oil pan cover in the photo that looks like a triangle shape. If it doesn't have that triangle line shape means its not LSD.
I cleaned, sand papered and paint it the differential today.