[daddy6stringer]

I would suggest not drilling it, unless you are absolutely sure of what you are doing. As a machinist I know all too well what can happen if your drill bit isn't right on size and location. If one cutting lip of the drill bit is even slightly different size from the other, you can run into the issues described in the previous post. Most drill bits also tend to drill a fair bit larger or smaller of their size, as well as out of round.
Although not a noticeable amount, it can make all the difference in the world.
If you are okay with doing it yourself, make sure you have the proper tools for the job, do it as accurately as you possibly can, take your time, and don't force the drill bit. Most importantly, don't run the drill press on too high of a speed. An edge finder would end up being your best bet, as the pointed end can be used to assist in locating the center position of the hole. Also, use V-blocks.

As an alternate solution, I would recommend removing material (very carefully) from the nubs that go into the cylinder head. Use some fine emery paper or whatever you have that will have a very slow material removal rate. You don't want to take off too much, or they will sit too loose. Just keep testing for a good fit.

Hope that helps...

D6S