Quote:

The machine marks suspicious.



They look factory to me

Concerning the Race Hemi Orange paint (which looks original) all 64-68 Hemis and SOME 69 Hemis were painted Race Hemi Orange. So, it's likely that it was built before the paint color change. As stated, it's most likely a typical service replacement engine of the era that was put into inventory and used when needed as a warranty replacement or simply sold over the counter, etc. The other stampings were added after the fact by whomever, without a paper trail the rest is pure speculation.