""C" heads are 56.  Assume they came on  272 as well as   292 and 312 as that is the usual.  Early C's had the core plugs at the ends, later ones did not.

54 Victoria 312;  48 Ford Conv 302, 56 Bird 312
Forever Ford
Midland Park, NJ

I am tearing down my 56 292 Motor to rebuild it. When I pulled the Motor  5 Years ago to re-seal and Paint it I pulled the Pan. Bearings are original Standard size Ford Bearings. The Timing Chain was just about falling off so I replaced. I thought this Engine was original based on the Bottom end. When I pulled the Heads this Wek imagine my surprise It had the bigger Intake Valves used on the 57 and later Engines. Heads are ECZ-C Heads. Actually pretty clean. I don't know if the Exhaust Valve Seats were done with Inserts Yet. I don't have a compressor to take One valve apart and check. There is minimal Ridge in the Cylinders. I have been picking up Parts for the last while anticipating doing rebuild including a full Set of New Valves including the bigger Intake Valves. The Block is 1956 based on date Code and uses the 3 different lengths of Head Bolts. What are the Heads? ECZ-C application. Obviously Someone has worked on this Motor in the Past but not the Bottom end. I am just doing a stock rebuild using a Overhaul Kit sold on Ebay. Quality Parts as I used One about 10 Years ago on my last rebuild.