I just replaced the Cam drive belt at the recommended 105,000 miles. I could not get the marks on the cam sprocket and crankshaft to line up exactly, it was always 1/2 tooth off. So, do I put the camshaft 1/2 tooth advanced, or 1/2 tooth retarded?

 

There should be only one way to put it on,but if you cant get it, Id say advance it to where it should be.
I bet its just the leading edge slack thats throwing you off...
Are you sure your using the right timing marks for your Cam drive belt?
I think different gens of single cams have slightly different marks...