1985 chevy 1500 won't idle

[looking4help]

I have recently bought a 1985 plow truck with a 350 engine. However, when I first drove the truck it stalled and would not start or charge. I proceeded to change the alternator and one gas line to the carburetor. After I did this the truck started but it will not idle, the only way I can keep it running is by giving it gas. Anything thoughts or ideas on what I can do?

It also stalls out when it's in gear and I'm not giving it gas. Thanks!