[dmsfrr]

Is the engine out of whatever car it was in?
Did those Ford guys give you any reasons for their conclusions?
Can you pass along any block and head casting numbers?
How about some almost close-up photos?
There are several specific external parts for engines that are actually out of 55/57 T-Birds... driver's side exhaust manifold, crankshaft damper pulley & timing pointer, water pump spacer, timing chain cover, motor mounts, thermostat housing, valley pan, oil pan, oil dipstick placement .....

Just FYI, there isn't a way to positively identify a 312 from the outside unless the oil pan or transmission is off. It will have 'ECZ' cast into the main bearing caps and an aspirin sized dot on the rear flange of the crank if it's a 312.