Just use a drill bit that will fit in the hole on the inner side of the clutch cover were the crank goes, that establishes were you need to be, then measure i think one and a half inches up on the other side of the cover, but following the oil galley up and drill your pilot hole.
Here is a oil galley diagram, #5 is the crank oil hole in the clutch cover.
If you follow the line in which the fitting go you'll notice the notch on the top of the cover, just stay in line with that and you'll be fine.