Sounds like one or both of your batteries are dead, hopefully just a loose connection at either the positive or ground posts. Go back to everything you did when you replaced the starter and make sure you put every thing you touched back in the right place.
If you have a voltmeter, pull the ground off one of the batteries and then check the voltage at both batteries. 12. 0 is a dead battery, 12. 3 is 50% charge. If they both show 12. 5 or better, then leave the one ground disconnected and turn on the headlights and cab fan on high and check the voltage of the one battery that is connected. Hopefully still somewhere around 12. 2 or more. Turn off everything and check the other battery by disconnecting the one ground and reconnecting the other, then turn the lights and fan back on. Poor mans way of doing a load test.
If you have a battery charger get it connected and get them back to full charge (presuming they are low), then see if she starts. If she does, verify that your alternator is working. Should see at least 13. 2 at idle.
Might also be a voltage drop somewhere between the two batteries and the starter. Google "Voltage Drop, Automotive Starter" and you should turn up several results on how to test.