were sodium filled exhaust valves ever discontinued by the factory?

This is a Dino question but I think there may be more folks on this forum who will know the answer to this question.

When I bought 02840 the story was that the PO had gone to Italy and gotten a bunch of NOS parts from the factory. Attached is a photo of a document dated September 1984 I have which would seem to support this.

My question is that the doc shows the part number for the "valvola scarico" as 106553.

The blue Nov 1970 Parts Catalog I have shows PN 4198464 for the "Valvola di scarico"

The paperwork from Ferrari of Los Gatos shows they used Intake valve 4178519, which is the PN the blue book shows. There is no charge for exhaust valves, presumably because they used the ones the PO had gotten.

So the question is, since the PN for the exhaust valve had changed and the intake had not, did Ferrari supercede the original failure-prone sodium filled exhaust valves with something better?

I don't want to pay to have my motor pulled apart to replace the exhaust valves only to find they aren't the failure-prone ones.

Thank you
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OOPPS-- I goofed.

Will one of the moderators please move this to the Vintage forum? (At least I think that would be where the most knowledge of '70's cars would be.)