GM-GMC: starter wiring, gm vehicle, gm vehicles

Question
I changed engines in my pickup.  My starter is not cranking.  I have the ignition wire and the power wire from battery to starter connected.  What other wire if any am I forgetting?

Answer
Generally there are ounly two wires on GM vehicles (I assume it is a GM vehicle) going to the starter.  One is a battery positive lead, which should have power at all times and the other is a smaller usually blue wire which is the solenoid control wire.  It should have power when the the key is in the start position.  Check to make sure both of those have the appropriate power at the appropriate times and go from there.  Is it possible the starter is defective?
Hope this helps.