Not entirely sure I understand your question but this is what I know:
1) The crank shaft front end belt pulley does as far as I can remember have a "nominal" TDC indication
2) on most Fiat flywheel housings (not sure if this applies to the Croma) there is a "window" vertically on top of the housing to positionally see the crank flywheel
3) The cam shaft timings have NO markings. You need to have the cam shaft timing "plunger" alignment tools to correctly position/time the cam shafts
Reading your post I think my 3) above answers your query?