I had a piece of road debris hit my header pipe hard enough to dent it and break an exhaust stud. I borrowed a 90 degree drill from work but I saw a 90 degree adapter, from Harbor Freight I think, for a lot less. I also kept pieces of a broken mirror that helped. I got real good working backwards. The stud is probably just sitting there and will probably come out real easy, probably, mine was. But I did have a bracket bolt in my iron block break, then break the ez-out too. I got that out with a Dremel and a thin chain sharpening stone. I got real good working through a mirror.

The hardest and most important thing is to get perfectly centered.