Odd scraping noise in recently rebuilt 383 (68 Charger)

[BrokenHero]

Engine was recently rebuilt and also tuned up, spark plugs regapped, carb adjusted, etc.
It started doing this out of nowhere, a few weeks ago. Rough scraping noise.
Any ideas? Short video link below.
Thanks
https://youtu.be/gBxt6ktV7TY

[Dodgecharger74]

check flex plate torque converter

[John_Kunkel]

Disconnect the fan belt temporarily to see if the noise stops.

[Alaskan_TA]

Converter bolt heads contacting the webbing at the back of the block is a possibility.

Were the correct factory type thin head bolts used? Were they all tightened correctly? If so, converter fully seated first?

Another possibility that can make that type of sound is a loose harmonic balancer.

[Just 6T9 CHGR]

Could even be the flexplate rubbing on the gravel shield (if you have it installed)