SVO stands for Special Vehicles Operations, it was the parts and performance arm that was the precurser to SVT (remember the SVO Mustang?).
The cover has many benefits. This cover is made of 356-T6 cast aluminum and offers better cooling properties over the stock stamped piece. It is also much stronger, due to the axle girdle and load bolts that support the differential bearing caps. The girdle's job is to span the width of the cover and keep pressure on the bearing caps to reduce distortion in the rear end during high load situations, such as drag racing, towing and off-roading. This deflection can cause your ring and pinion teeth to chip and shorten their lifespan. As a side benefit to those do-it-yourselfers, the cover also incorporates both fill and drain plugs in its design, so that the cover never has to be removed for the differential to be serviced. And of course it looks great.
I use 75/140 synthetic (what Ford calls for). The seeps come from every bolt on the back. I used teflon tape on the lower bolts, and on the fill and drain plug, along with the bearing jam nuts.
Hasn't seeped since.
--Sean