I had a Shadow and the new transmission/convertor had no TDC mark.

Since it was not a race engine, just a commuter.
Also the engine really only needs you to set the ignition timing as reference. I didn't feel accuracy was that important.

I did the backyard method of looking for TDC feeling for the piston coming up. Made a mark with a paint marker. Did it again on the other side. In between my marks was TDC or close enough.