there is a good chance its throttle body which is desirable for a 4x4 because it can be limped home still if fuel pump dies
just check for rust... rear leaf spring mounts have a tendency to rust out.. if it is a new one installed is $200 so get price lowered by at least $250
(unless of course its already dirt cheap)
I wouldn't pay more than $1000 for one, I payed $700 for a '94 F-250 that had nothing wrong except a leaky exhaust(no dents etc) I bought a '92 F-250 for $400 that only had 60,000k on it and sitting in a garage for 10yrs(replaced fuel pump and ran like new).. also bought a '98 F-150 for $400 that just needed a clutch(drove it home) all these where off Craigslist so deals are out there.
Keep in mind all my purchases where stock trucks.