Here you go. Check this link out and you will find tons of very good information. There are others but I need to look more in the hard drive. I know Scott at Brillelli changed the ports on the 2 barrel Toro's he was doing. I have played with it some but have always been pleased with the performance of my favorite conversion engines, those being Echo. You can use an end mill or a Dremel tool depending on what you are doing.

http://www.edj.net/2stroke/jennings/