Depending on the year of manufacture, there are several flywheel marks. All of them are close to top dead center, but not necessarily exact. The only way to know for sure which is which is to use a degree wheel mounted to the crankshaft while the engine is being assembled, and physically check each one. There is a way to establish true TDC with the cylinder head on the engine, but I'm not going to try to explain it online. Call me!
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!