Stefano, I have no doubt that is an original deck and assembly stamp, indicating standard trans with 3x2s (280hp). The tri-power set-up appears completely correct with the exception of the replaced fuel lines and center 'T' fitting. The plug wires should have 90s at the distributor and 15deg bends at the plugs. The LH valve cover is incorrect. The rear wire loom should be low on all 3x2 motors. I couldn't quite determine the height of the RH cover loom in the photo. There appears to be a patch panel on the firewall where an airconditioning plenum may have been. There may be an indication on the cowl tag if the car originally had A/C. The other engine compartment features appear to be correct.
I hope this helps.
Verne