Ok double checked on the 318. Sure enough it too is the same as the results you guys got. That being the timing mark is 5-6 degrees BTDC from the keyway........
Not sure why the engineers decided that's where to put the key, but I'm going to assume they had a reason for where the did it.
In my small mind, it would seem to me they could have put it anywhere in the 360 degrees of the crank snout, and just changed the location of the key way in the cam gear.