I’m reinstalling the engine accessories and I have three plates and can’t recall the correct one for a 351C. The engine is a Boss 351 and I wouldn’t know if the plate is different just due to that.
I believe the one wrapped up is actually a commercial/industrial application for the windsor platform, but is useable-at least it looks like the one I have
Whichever of the two manual plates you use, make sure the starter location and bolt pattern matches your bellhousing. The small bottom bolts moved around depending on the application.