Engine wont start, what now

[Brandonrescue]

hey i have a 68 firebird with a late 80's early 90's motor. The engine simply seems to have a problem whenever I start it up. The needle tach will jump all over the place and the motor will also sputter and do the same. It dies if i take my foot off the pedal. Now i changed the rotor, cap, spark plugs, and had the carb rebuilt. idk what their is next i can do! Odd thing though is even while its sputtering i quickly take it out of the driveway, put it in drive and hit the gas, while i am driving down the road the RPM tach and the engine will jump and sputter less and less, then after a few minutes of driving it goes away. The past few weeks though it has gotten WORSE. Now it will start for a few seconds without the RPM needle jumping(bascially running normal), then after 10 seconds it jumps and the symptoms start, then it dies. At this point, the engine wont start even after i put starter fluid in the carb. I wait about an hour and then it starts right up(sometimes). Idk what to do next. Distributor? maybe vacuum leak? Carb could just be shot? What doesnt make sense is that this is intermittent. I drove it fine all day yesterday after it did these symptoms early in the morning. Here are links of the video of my car to show you what i am talking about.

http://www.youtube.com/watch?v=2z7Ipy81Up4