k-1500 rear end

I have a 1989 chevy 1500 Z-71 and i was wondering was gears are in the rear end can someone please help me???

your vehicle has rpo codes in the glove box-a dealership can tell you what is factory-but if you do a basic rear diff. service and look on the crown gear it will tell you-for example a 12:41 is 3.42:1 ratio.