1978 Ford F-150 Won't stay running.

When I try to start my truck, I have to keep my foot on the gas. Once it is running it seems to be lacking power, and sputters when i give it a little gas or it cuts off completely. If i put the truck into drive it cuts off almost immediatley. I need your help since this the only mode of transportation I have to get to and from work everyday. Public transportation doesn't go anywhere near my place of employment.