With the crankshaft damper reading O degrees, and with the presumption that you are on the compression stroke, you can look at the tower for the #1 cam bearing. There is a mark on this tower and it should precisely align with the notch in the thrust washer that lives behind the cam sprocket.

I'm thinking that you possibly set the sprocket back on the camshaft with the crankshaft at 0 degrees, but with the #1 cylinder at the top of the exhaust stroke. I think it's possible to install the washer with the notch off by 180 degrees, so this would cause the problem that you currently have.