The last time I had to do this was around 40 years ago and I used a high quality drill press on the slowest speed possible (around 100~150 rpm) with a masonry drill bit. The more speed you use, the less likely your chance of success will be. The larger the size of the hole, the less likely your chance of success will be. If you're using a handheld drill it will never work for you. If you're using a cheapo Chinese Harbor Fright drill press all you'll do is shake it apart and you might break the bit. Probably a cutting torch would be better. Good luck.

~ Jon
1952 1/2 ton with 1959 235 | T5 with 3.07 rear end