Honestly you're not giving us enough info.
Diagnose it in the following manner.
1. Does the engine run smooth when you have to hold the throttle for it to run and how much throttle to make it run are we talking about?
2. Did you pull the idle air needles out when you rebuilt?
3. If so how many turns out did you set the needles?
4. Did you check to make sure the plug wires are on the correct plugs?
5. Is the choke open or closed when it dies?
6. Can you close the choke and make it run?
7. Is it a manual or automatic choke?
8. Does it die immediately or stumble to till it dies?
9. Are all the vacuum holes in the carb, that you are not using, plugged or capped?
10. What kind of carb are we even talking about?
11. Does it have manual or power brakes?
I'm still leaning towards a serious vacuum leak.
Take 4 pics of the carb and post them so we can see it. Front, drivers side, passenger side and one from the back.