yes it is open and it is s chassis, and depending on what driveshaft you have might not work
even though everyone says they are bad get a j30 diff and axle, from my pointe of view , changing the fluid in them with the proper oil they have not been abused like any s chassis diff
welded diffs are good for track but on the street they get annoying and call to much attention, we already have police attention why give them another reason to piss one off and have him pull you over, besides the tire wear is increased and its geting harder to find decent tires for cheap now