Thedriftbadger

Can't get my 05 g35 rev-up to start. Here's the backstory of the car; I bought it for next to nothing after the previous owner tried to change the head gaskets, failed, and gave up. So i tore the motor back apart, replaced everything the po did, entire top end. Everything done according to the fsm. Went together fine, has compression, timing is right. Will crank all day long with not even a hint of trying to start, no spark, no injector pulse.
Now, the thing is I've never seen the car run, so i'm really starting from nothing here. I don't know if it died while driving, or if the head gaskets were even bad to begin with. No codes either, so that's helpful.
Possible causes: crank angle sensor, flywheel installed wrong, bad ecu, security problem. Anything else?
I've read a million threads about security problems with these cars. Seems like it's very common. Everyone says the security light will stay on if it's a problem. Mine never comes on at all, so i don't even know if the light works. The car also has an aftermarket replacement key. So that whole situation is a mess in itself.
My question is, is there anyway to know for fact whether it's a security issue? I'd really hate to tow this thing to the dealer for them to tell me it's fine.
Thanks in advance