Pull all the plugs. Take a piece of wire or coat-hanger and bend it and put it in the spark plug hole so it contacts the piston. grab the fan with a hand on the belt for tension and rotate the fan/engine while a buddy holds the wire. you will be able to tell when you pass over TDC by observing the wire. Backup if required.
If you want to be really accurate, pull the flywheel cover and count teeth.
Kurt
