Craig
I am certainly no expert on flywheels and clutches but be very careful drilling a flywheel. If you are off by even a few thousands of an inch, you will almost certainly have a vibration. If you go this route make sure that it is done by someone that has lots of experience in this area. This is not an easy thing to do. You maybe better off to just buy a new flywheel, more dollars but less problems later on.
Good luck,
Wayne