truck wont stay running while driving

[1972BackInBlackC10]

i hope you all can help as i dont know what to do anymore, my truck starts and runs fine even when you put it into drive it stays running, but when you get about a block distance or more it seems like its losing power and when you give it gas it tries to die or just dies completely

once you start it again it just wants to do it right away when u start driving, the truck has a brand new carb on it, it was doing it with the old one too, new spark plugs, wires, cap and rotor, the amp gauge shows a good charge so the alt and battery should be good and iv checked all my vac lines and it has gas i checked lol and added more

what else am i missing? any ideas???