Check small trigger wire in RUN position.
If it doesn't have 12v then you're right, you got to back up to figure out why.
If it DOES have 12v, then why isn't it cranking the engine?....
bad ground back to battery?
bad positive connection from battery?
engine locked up? Can you turn it by hand?

 

I will check the voltage to the starter. I cleaned the battery connections and put some electrolytic grease on them. I don't remove the positive, i just remove the negative. I have to keep removing it to turn off the dash lights or it will stay on and drain the battery. I have checked the battery and the battery posts to make sure I am getting a good connection, am consistently getting 12.5 volts or more. Engine is not locked. I have been turning it by hand during install.

 

ah sorry man. Sounds like I'm going down the wrong path here.
So you pull the key out of the ignition and the dash still stays on?
Just reread your first post. Just throwing things out there...any damage done to the steering column during R&R?
Somebody here probably knows what module lights the dash in a 2005.

Earlier you said you found a ground wire smashed. Had you applied voltage/tried to start before or after you found that?

 

Maybe a dumb question but did you check all your fuses? I don't mean just look but check them for continuity. Make sure your relays are also good.

 

System main power wire fusable link ? not sure if they still use them but many a Chevy Pickup used to come in on a tow truck because of them. it used to be in the harness on the firewall you could find it about center of the cowl usually outside of the wire bundle, typically white or yellow.. They are crimped in.. I used to replace them with a breaker.. Its basically a fuse for the starting solenoid circuit.. Bad starter solenoid usually popped them.

 

I have great news!!!! Figured it out. It was that ground #103. It must ground the climate control or something. It is over on the passenger side just below where the coolant lines go into the fire wall. It was stuffed up behind those lines and i couldn't see the end. After I saw that diagram i went looking for a ground wire over in that area. Didn't see anything at first but tugged on that wire and it fell out. Ground it to the block and she fired right up!!!!
Thank you all for all your help. You were all awesome! This is a great forum and i'm sure I will be asking many more questions. I still have to tune it. It doesn't idle very well, but will figure that out later. Just glad to have it started. And then I am building another LS to put into my 66 impala. I can't thank you all enough.

 

Cool! Gotta be a massive load off your mind! Glad you got it fixed!

 

yep, feels good to hear it fire the first time.
Let er rip

 

Usually is something simple. Congrats