I like to go a little crazy when marking my flywheels and use a sharpie to mark TDC for each of the cylinder pairs. Here is the writeup:

http://devestechnet.com/Home/Flywheel

It will depend on the number of teeth on your flywheel. I have a 261 in an AD with the 6 volt flywheel, so I have to count differently. Hope it helps!