Broken studs slant 6 ex manifold

My original manifold had deep pits and damaged studs. So I got another one at a local U-pull. After an hour in the hot sun getting it and a couple more hours trying to fix it, I gave up and bought a new one. I think I had every hole EITHER straight or centered, but none were both. LOL

To answer your question, Best thing I would say is set up something as a guide for your bit . It's pretty far through there and needs to align with the intake above and the linkage bracket holes underneath.