1969 C20 rear axle; what were the options??

[VTKidder]

I'm looking at a '69 longbox pickup, 3/4 ton, 2WD, 307 with 4-speed floor shift transmission, 16" wheels, power drum brakes all the way around. The rear suspension is trailing arms with coil springs. I was unable to look in the glovebox for the RPO codes to indicate what rear end the truck has, but the rear end is very large, and has a drain plug right in the back of it. What were the options for rear ends, and ratios on a '69 3/4 ton with the 307??? Thanks!

-adam