1958 4WD 1/2 Ton Questions

[RShaips]

I saw a truck today that looked to be an original 1958 4WD. Looks to be all there, same owner for 35 years and says it's an original 4WD. What year did GM start making them instead of NAPCO? What do you think it is worth in this condition? Pretty rough shape but he did say the motor was replaced with a 235 from a car, that should run if messed with. Left front axle and front driveshaft is out. I would appreciate some feedback, last thing I need but I think I am going to buy it. Thanks