Stalling at idle; advice needed

[oneday1]

Truck is a 1978 350/th350 C15 "Heavy Half" so no smog stuff, carburated.
I have searched the forums and found many somewhat similar scenarios but not exactly like what is happening to me.
Truck will start and drive fine, but when coasting for a while or sitting at a light it will start to sputter and die unless gas is pressed. Doesn't take much, just enough to keep the rpms up and it won't die and then when given more gas gets up to speed with plenty of power and will drive for at least an hour (just tried) without ever dying as long as it isn't allowed to throttle all the way down. It seems it could be anything from dirty spark plugs to vacuum leak to distributor to fuel pump to carb etc.

Has anyone experienced this symptom? Have any luck fixing it? Any help is greatly appreciated as winter is here now and light is limited. Thanks in advance!