You might need to be more specific. But it is a differential which has 4 gears I believe. If your talking about gear ratio. I'm not really sure on your particular vehicle but you could always take off the cover and count the teeth on the gears.
it all comes down to what motor you have what trans and wut gears you have in your rear end
Rear end of the engine - front end of the transmission
prolly not
Should be on the rear lower end of engine--follow + Battery cable
Im pretty sure it 4.10:1
in my 91 is 30 gal
Should be at the lower rear end of the engine - follow the cable from starter solenoid
They are all different. try looking in the glove box it might say in there.
The Cheyenne is a base model compaered to the Silverado. Excluding power windows, power locks, tilt wheel, and interior carpet. my 91 1500 Cheyenne has tilt & cruise from the factory.
Yes. 91-96 impala, roadmaster, caprice, and fleetwood rear end are all the same and will fit with no modifications.
Timing chain
yes. The only difference may be the gear ratio which could affect your speedometer accuracy