1984 Nissan Truck

I have a 1984 Nissan/Datsun 4x4 truck with a z24 4cyl engine and less than 500 miles on it(The engine is newer but still carburated.) It was rebuilt and overhauled, then sat for 8 years in my grandpas yard. I cranked it up. It ran fine, even without the vaccum assist line. But just recently it will always die if driving above 1900 rpms. It will, however, idle and run fine up to 6000 rpms while in neutral. Takes off fine, until 2000 rpms then starts to spit and sputter and put out a lot of smoke then try to die on me. I got it stuck the other day and managed to get it out in reverse. Strangley it dies in 1st gear uphill. The spark plugs are fine, no water in the gas, vaccum lines are in the right spot, but will not go above 2000 rpms while driving, even with the pedal to the floor. Ive noticed the distributor is all the way to one side, but it wont run in any other position. Any Solutions?
April 23, 2007.

Could be the choke binding and not widely opening when it supppose to.

Apr 23, 2007.
I've almost fixed it, turns out to be a combination of problems. The choke is fine, but my fuel filter was really nasty (i dumped nasty red and black stuff out of it) so I replaced it. I also found that it had bad ground, so I put a wire from the battery to the frame and motor. It runs fine now. I guess the distributor couldn't pull enough power for the spark.

Apr 24, 2007.