OK , first off no pictures , it sounds like a dandy truck here is my take on it (YOU ASKED)
I would inspect the truck underneath if the cab supports and floor pans are good and the frame is clean and it runs and drives good I would say (WITH NO PICS) $3500 the $4500 price would be fine if it was a fleetside the stepside takes off the value , it sounds like a great truck if you get it post some pics !