Sounds good, almost too good. only 50K miles on a truck that's 8 years old? As we can all attest, I look for any excuse to drive my truck anywhere. If that mileage is true, the owner only drove 521 miles a month or 6,250 miles a year. Hey it could happen, but I'd be suspicious. Go over it with a fine toothed comb. If all seems to check out, I think the price is within reason.
-scott