No start on rebuilt 360LA

Yes both valve covers off, checked 1 and 6 both were as you said. 1 closed and 1 ready to fire. Set distributor to #1 +-0-15 that’s when we saw the fireballs. Plug wires are all good, correct firing order checked 69 times.
Now you have me stumped. I want to know whats wrong with it. Lol