FEPASA CM1800C D-1820Rio Blanco Rio Blanco

@fepsa6600 Hello! Are you sure this is U18C? Looks like U9C

When built in 1957, the whole series was U9C, 900HP. After FEPASA taking over, these two locomotives were re-engined at Casagrande Motori shops, in Chile. The new engine has 1800HP, for that reason the locomotives were renumbered from original series Dt9000 to this D1820, reflecting the current power. Unfortunately there's not much info for these locomotives available in the internet.

Only two units were converted 1820&1821 according to this listing. Is this correct?
https://www.thedieselshop.us/Chile-FEPASA.HTML

Can you suggest a class name for these converted locos? U18C looks strange because they have different bodies.

Yes, only two units converted.
I see your point on the denomination. I was not aware of the CM1800C denomination, it may be the correct one.