Here's a link to a tech page showing the 2 types of sure grips Mopar used through 1974. Be aware that the first one is the cone type and they are not considered rebuildable, although if their not worn real bad you can machine the cones down to make them work again. But sometimes their completely worn out inside and their basically junk. Just tossed one like that a few weeks ago. If the one your looking at turns out to be a cone type don't pay much for it unless the seller proves it's not junk.
The one in the bottom picture is the clutch type and is rebuildable and much heavier duty (4 spider gears vs. 2 on a cone type). It is the sure grip of choice IMO...
http://www.moparts.org/Tech/Archive/axle/13.html
I can't find a good picture of an open differential. Here's a link to a page showing an exploded view with an open differential but it's not the easiest to picture since everything is disassembled
http://www.moparts.org/Tech/Archive/axle/9.html