TBI Manifold Bolt Holes - anyone machined em?

[cruiser enthuiser]

I'm starting on a tbi conversion for my 350. I was initially under the impression that I would have to take the manifold to a machine shop to have the four center bolt holes elongated to fit my non TBI head. After doing some reading I see that some guys have drilled them themselves.

Can anyone with experience doing this comment here and give me some advice. I'm reluctant to just eyeball it or trial and error it but if I can save some $$ and DIY it I'd like to.

Thanks.