Converting a D4 to electric start

I was wondering if anyone has recommendations on where to find a good hole saw to cut a hole for a starter in the bell housing, I would appreciate all the advice that I can get

Thanks
Pat Bayer

http://www.lenoxtools.com/Pages/Product.aspx?productId=CarbideTippedHolesaws I've done two conversions on D4's and a carbide tipped saw is the way to go. Took about an hour and a pint of cutting juice to go through. For the first one I used one that I got at a hardware store, a high speed steel one and it took a while to wear it's way through an inch of cast iron, plus I had to resharpen it twice. A good heavy half inch drill motor is a minimum, a 3/4" drill motor would be better.