The valve covers aren’t OEM for a Cobra. I don’t think that style was used except for over the counter. Same for the
oil pan.
Side oilers have value, but not as much as some think. After market blocks are better. The value is in restorations or a guy that wants a Ford block for a Cobra build.
A quality OEM side oiler build is worth maybe just under $20k. Your value is the casting number and date code. If it helps someone complete a Thunderbolt restoration it is worth a lot to them.
John