Maybe it's not yet replaced.
Have seen this nylon gear on into the past rebuild engines too .
For be sure check this.
You can check the wearing when you try to rotate the cranck l+R , on the circumference I can be 10-12 mm , if it's more better replace the timing gear and chain.
Simon
@S.Hafsmo posted:Would the '78 have the nylon coated timing gears?