Replaced starter . It cranks but car wont fire has fuel. Where do I start? Looking

It would be helpful to know what the current state of the engine is such did it run before you replace the starter?

The first thing I would check would be to see if you're getting spark. When will you can do that is to use an inline bulb that are relatively cheap to buy and are set up to go in series with a spark plug wire. Another would be to pull a plug and make sure it is grounded and see if you're getting spark on it.

Agree.  Sounds like no spark.  Check the wiring from coil and check the points and condenser.

Nice stable of cars too!

Did the car start and run BEFORE you changed the starter? That's an important bit of information needed to help diagnose the issue. If was able to run before, then I would suspect a wire on the starter solenoid has been misplaced, or left off. If this is a true/stock LS-6, I assume it has the transistor ignition? Can you confirm or deny that it does?

Non TI ignition will have a yellow wire attached to the outside terminal of the starter solenoid. This feeds 12v to the coil while cranking. If this wire is left off, or installed on the "S" terminal of the solenoid, it will not start. The "S" terminal, which is the terminal closest to the engine block should have a purple wire on it. This is the "Start" signal from the ignition switch, thru the neutral safety switch. 

Along with the large battery cable, there is a smaller, red wire attached to the large terminal of the solenoid. This is, obviously, battery power for the starter, but the smaller red wire, and it goes thru a brown fuse-able link, then on to the horn relay on the driver side fenderwell. This distributes battery power to other areas of the car.