This is a 351 Cleveland block plate and matching thermostat. The 351C does NOT have a coolant bypass hose like other V8 engines from the period.
Instead an internal block plate allows coolant to circulate in the engine block when cold and this stops when the thermostat opens and seals the hole in the block plate. If you are missing the block plate or the correct thermostat, your engine will likely overheat. This is a common Cleveland issue.
Since block plates are long discontinued by Ford and costly and hard to find in NOS, this thermostat and block plate are designed to solve your needs. Remove the block plate if it exists and replace with the one from this kit and then install the thermostat and then bolt on the water neck and your problem will likely be solved. Please note there are other cooling issues that Clevelands and other Fords have that will require further investigation if needed. This item will fit ALL models with the 351 Cleveland Engine such as Mercury Cougar, Torino, Ranchero, Cyclone, etc. Please review pictures and what you require if you are unsure. Please read description before asking questions. We use Ford factory microfiche to decode parts. Parts are new original Ford parts unless otherwise noted. We stock 1000's of NOS Ford parts. We also always have an assortment of rare good used Ford, Lincoln, & Mercury Parts. An assortment of Goodyear & Nascar collectibles are also in stock. We will try to keep you up to date when this occurs. Remember to check out My Other Items.The item "Ford 351C Cleveland Thermostat & BLOCK Plate Mustang PANTERA Galaxie Torino" is in sale since Thursday, September 12, 2019. This item is in the category "eBay Motors\Parts & Accessories\Vintage Car & Truck Parts\Cooling System". The seller is "machviii" and is located in Vincentown, New Jersey. This item can be shipped worldwide.