This differential will be in any manual that is available for the car.
If you can find out what Diff it is (8 bolt 12 bolt and so on) there are several part supply outfits on line that have parts diagram exploded views on PDF format.
No, the chevelle isn't as wide as the impala, you would have to get a rear end from a full sized Pontiac or olds.
That all depends on the rear gearing in your car and the size of your engine.
The rear outside axle seal on my 1968 Chevelle has on it's outside face, the number 3832418. I am not sure if GM uses this same number for their parts inventory, but the manufacturer of the seal does.
21/4 pints and do Not forget the additive if it is limited slip.
Depends on the rear axle the car has. 10 bolt is most likely 8.25" for a 1968, but 8'5" is also possible. 12 Bolt is 8.875".
A rear end from ANY 1968-1972 GM A body will bolt right in.
Not without some serious modification. Chevelles had a coil spring rear suspension while the S-10 uses leaf springs. While I haven't measured, I'm pretty sure the Chevelle rear end is also wider than an S-10 rear end. Now, you COULD change the spring mounts and narrow the Chevelle rear end to fit, but there are alternatives that would be MUCH easier to use in an S-10.
Depending on the rear gear ratio which is usually a 3.31 you should get about 12 to 14 MPG if you keep your foot out of it.
find a Chevy 12 bolt rear end or a built up 8.5 rear end.
LS6 Chevelles had rear disc-brakes
You can get and exploded view of the 1987 Chevrolet rear brake assembly and most Chevrolet dealerships. Most local libraries will have service manuals with the exploded rear brake assembly view.
No it will not.