1965 Valiant 200 convertible (minor project)

Can you explain what you mean by correct base? You mean the hole is sized for a 1 bbl, 2bbl, 4bbl, etc, and the upper cover part is the same?

I like the idea of the ribbed valve cover and a nicer air filter. Looks better but still stock.

Yes. Factory made one barrel and small-neck four barrel bases for that top. For two barrels and large-neck four barrels (pretty much all currently available four barrel carbs, as well as Holley two barrels) you just adapt your own. On my 56 Plymouth with an Edelbrock carb, I used the base of a 10 inch chrome air cleaner. Fits closely enough.

Valve cover is an Offenhauser. First offered in 60-61 for slant sixes and still available new today. It's cast aluminum and seals to the head better than a stamped steel factory cover.