Jason, You are not the first to ask. My opinion, a custom made part to get by some modern vintage race organization rules or another. With custom vintage race transmissions, differential housings, cylinder blocks, cylinder heads, and multiple 4V intake manifolds floating around why not an IR 8V intake? There is a Ronwill speed parts and racing business in Sweden. I sent them an inquiry and got no reply.
http://www.ronwill.se/index.php?menuitem=1
C4OZ-6B068-C was a Ford Motor Company sales, not engineering, number for the entire 8V induction kit early in 1963 into 1964 using 4 each 48 IDM1 or 48 IDM5 carburetors, all the brackets, all the linkage, and the water neck / fuel log to take out of the box and install on a Cobra. The advertised suggested retail price was $1,230.70. There were new economy type cars for sale in that price territory.
S1CR-9423 was the Shelby American sales number for the final "COBRA" version of induction kit using 4 each 48 IDA or IDA1 carburetors. The kit was aimed at racers in general and not Cobras as the layout was not submitted to or approved by the FIA for Cobra roadsters. This kit did not have everything required to outfit any kind of racer; did have a GeonŽ instruction booklet, water hoses, water hose clamps, and gaskets. The suggested retail price was $595.00. This version of kit was sold into 1967. Dean Moon sold the exact same kit under his sales number MWM-101. It was replaced by a similar kit in mid 1967 under number SFJK-9510-E with a “SHELBY” lettered intake. Lincoln-Mercury sold a similar kit in 1967 under number S7WK-9423 with a “COUGAR” lettered intake. All versions had a suggested retail price of $595.00.
The casting in question combines sales numbers for induction kits into one part mixing 1963 and 1965/67 marketing into one item. Somehow they missed the number for 1964-65 FIA approved for Cobras system kit under Ford sales number C5OZ-6B068-A using 48 IDA/IDA1 carburetors; this kit did not have everything required to outfit a Cobra; suggested retail price of $695.00.
The RONWILL name and other number cast in mean nothing to me except there is a speed parts business over seas that race prepares Fords by that name.
The boss for the thermostat housing is machined in the style Ford converted to roughly March 1965 (Thank you Bob Mannel's book for that detail.), which requires the correct thermostat water neck to go with it.
The size of water passages are very much larger and shaped differently than any of the known factory COBRA/SHELBY/COUGAR/FAV/Ford SK/FoMoCo intakes for 4-2V.