GM-GMC: 95 gmc has no snap off a stop but is fine once it gets going, gmc sierra, hiway

Question
I just bought a 95 GMC sierra 1500 4x4 5.7L V8, it has 197000 miles on it and the guys said that reverse didn't work when he got it but he had it rebuilt.  I just changed the plugs and they NEEDED it bad, the wires look good though.  My problem is that I try to take off from a stop and it chugs pretty bad and doesn't want to get going until you get it rolling.  then on the highway its great it rides smooth and shifts fine, feels like it shifts fine at slower speeds too.  In reverse, its got a hell of a lot more snap to it than when its in drive!  got any ideas I can start with?  Thanks for any information you give me, I need at least a starting point.

Answer
Is it possible that your tranny is not shifting down into first gear?  If you are stuck in third gear and try to accelerate, usually it is really crappy performance.  If the engine runs fine, revs out in neurtral, runs ok on the hiway, no problems in reverse, I kinda think it may be a transmission shifting problem.  Try selecting first gear manually and accelerating from a stop.  If it better, get your tranny checked.  If it is no better, hmmm, still get your tranny checked.
Hope this helps.