Gear ratios vary. Most autos were 4.63 and manual were 5.12.
Front can be used in either front or rear just have to match the side gears up if using the whole chunk. There is a split down the middle for people using the aluminum third housing versus pulling the gears and using the samurai steel housings. Your later GVs come with a steel housing.
Four door from 91 or 92 till 97-98 is the 16v multi port injection
Two door from late 94 CA. manual transmission vehilces and all after 95 were the 16v multi port.
The engines are easy to tell apart. The 8v looks similar to the 1.3l samurai engine, just look at the valve cover. The 16v has a much larger intake setup and a fuel rail. Also the vavle cover is more flat, brown and has the spark plug wires leading into it.
This is very basic and generic information at best.