You have a truck that is in the last generation (1968-1972) of collectable Chevy pickups. The mileage is good. The value will be largely determined by features, options, trim line, and condition. In a very general way, the v-8s are more desirable, and the stepsides are worth more. The 4x4 is a plus. Rust is the biggest enemy of these trucks and hurts their value the most.
If the truck is real nice, consider hiring an appraiser. Small differences in condition can make big differences in value. You can also check ebay for actual selling prices (click on "completed sales" for '68-'72 only when you do a search).
Even if the condition is less than good, you will have no problem selling this truck. Collectors or restorers won't touch a '73, but will be interested in your '71.