I have about had it with this engine. Strange vaccum leaks, not runing right, heavy shift. The engine is suppost to be a rebuilt when I bought it, But I have no idea now. Ok now for the questions.

1. what parts on a 2.8 v6 are interchangable with a 3.1 or 3.4v6?
2. Does any one in or around Dallas, Texas know where I can get a used v6 engine in some what decent shape.
3. Any one in or around Dallas, Texas able to help me Diagnos the problem

Some one please help me bring my firebird back to its glory so it can stop acting like a fire chicken

 

You're on a very wise course of action, planning and problem solving before you replace your engine.
Vacuum leaks are common as hens teeth. Spend a whole day solving them and lots of problem may disappear.
Best way to solve the vacuum leaks is by removing the upper intake, twist/flip over to passenger side of engine, then go to work.
main problem area is the main PVC set up based at base of distributor, driver side. That hose is 1/2" THICK WALLED heater core hose, a short section (about 1-2" inches). That is main vacuum source. it's tough to do this work and lots of parts break.
Use 5/16" windshield wiper hose to repair hard plastic line cracks.
Work forward from all vacuum leaks solved.
How to know if your engine is "good" Compresison test. Look for readings over 100 PSI per cylinder. The higher a reading towards 175/200 PSI indicate a decent engine.
Hard shifting is TVC cable adjustment. I know. Just had mine readjusted. Shifts slightly harder, now.