I am putting a two groove crank pulley on my motor and one of the holes doesn't line up. Can I just drill the one out that isn't lining up correctly? Is the pattern different on these from year to year?

I had a similar situation when I purchased an underdrive crank pulley for my '66 383. Some dampers had a bolt pattern where all six holes were evenly separated "symetric" and others were "asymetric". My crank dampner was asymetric and my new pulley was symetric.

What I did was overlay the new pulley over the original pulley and rotated them until all holes lined up except for one. At that spot I elongated the hole (in the new pulley)
so that the last bolt will go through.

As said just file the hole a bit.My March pulleys have one hole elongated from factory to compensate.Rocky

They changed the pulley bolt configuration in the early 70's?. Not a big deal - file it out. It is only one that is off.