Starts then dies

[Yurchaka1]

I have a 65 C10 with a 230 straight 6 that will fire up but then die after just a few seconds. Last week it wouldn't start at all and I noticed that my fuel filter was empty when cranking and diagnosed the fuel pump as bad. I put in a Carter M4503 fuel pump and replaced the rubber fuel lines and it started up. Few days later I went to start it and it died a few seconds after starting. If I give it some gas it'll last a few seconds longer but not much. I replaced the fuel filter which was horrible but didn't help. I confirmed gas is getting all the way to the carb (Rochester B). I also tried to pour some gas directly into the carb while my wife started it but that didn't help either. I've always had to full choke it to start and keep about halfway to a quarter on to prevent stalling out at red lights so I'm thinking the carb is clogged and maybe needs a rebuild.

I'd really appreciate any thoughts or suggestions to confirm or deny what I'm thinking.