Truck keeps dying??

[danheit]

Bought the 71 C10 last night, stock 350/350. Drove 90 miles home last night no problem. Drove to breakfast this morning, no problem. Started driving home from breakfast, truck was lacking power, died going up a hill. Started right back up, but cut off several more times before the battery finally died. Get towed home and find that the alternator belt had about 2+ inches of movement. Tightened it up, charged the battery, started right up. Went to drive to the auto parts store to get the alternator tested, cut off on the main road just outside my neighborhood. Right before the trucks cuts off, you can feel a loss of power. I initially thought it was a fuel delivery issue, but it's not. Definitely something to do with the power. Any ideas? Going to get the alt checked now.....