Auto Parts: Chevrolet 4.3 liter V-6, chevy 1500, balance shaft

Question
QUESTION: I have a 95 chevy 1500 with a bad motor.  Would like to replace it with a used engine but with the many changes to the 4.3 I am having difficulty getting straight answers as to what year engine in compatable.  Mine has CPI and an aluminum pan.  Don't what to change computers.  Wouldn't mind changing intake and oil pan if necessary.  What engines would be most compatable (year wise)  Hope you can help
Thanks


ANSWER:      93-95 are the years you should be looking at.  The earlier engines don't have the balance shaft, and the later ones have different cylinder heads.

---------- FOLLOW-UP ----------

QUESTION: This truck although built in 95 is registered as a 96.  It does not have the "saw tooth" castings on the heads, I assume the 93-95 4.3 is still the best bet.  Is there any way to determine if it has CPI v/s SCPI?  Thanks, your previous response was spot on.  This is just to clear up some additional questions.  I have located a 93 low milage at a fair price and plan to install it unless you think I should be looking for a 96 up engine.

Answer
    If the truck is registered as a '96, then it is a '96.  I can't tell you how may times I sold people the wrong parts because they were going by the date on the door instead of the model year.  They start building '96's in July of '95 so that they can have them in the showroom by September, which is when the new models are supposed to come out.  So, unless the parts guy specifically asks you for the date on the door, go by the registration.
    The 4.3 from '96 to 2002 is basically the same engine and they should be interchangeable.  This does NOT apply to the 4.3 in the S10.  It has a lot of differences and is rated at a lower horsepower.  So, it sounds like you have more years to choose from.  The '96 and up engines should all have the SCPI system.  Somewhere on the engine there should be sticker that claims to be a Vortec engine.  The '95 and earlier were not Vortec and had the CPI system.  Another easy thing to spot is that the CPI engines had a two piece manifold made of aluminum but the SCPI engines had a two piece manifold with the upper half made of plastic.