maiden voyage- FAIL!

[HalfTon]

Well today was supposed to be the day my truck was to make the 15 mile journey home. The truck was at my grandpas shop were ive been working on it for the past few months. I had driven the truck up and down the road a few times around the shop but not very far and it seemed to run good. So this afternoon I went and fired the truck up, checked everything over and all was working as it should. I had a relative follow me just in case something did happen. So I left the shop happy as can be, got on the highway for about 1 mile and all the sudden it started sputtering so I pulled off the highway and saw the gas gauge was on empty. It had more than a 1/4 tank when I left. So my relative went and got a 5 gallon gas can and filled it up. Once all 5 gallons were in the truck I knew I had plenty of gas to get home. The truck started up just fine and drove good for another 1/2 mile on the highway were it started sputtering again while goin up hill, so I pulled off the the side and sat there trying to start it for a good 20min, I rolled back down the side of the highway to were it was more flat and it started back up again. By now I knew it wasnt goin to make it home so I turned around and started back for the shop. Then while on flat ground it started sputtering again and died at every stop light. I was pissed at this point and finally sputtered and chugged its way into the shops parking lot. What could be causing this? It ran fine when I test drove it and never acted like this?