Your VIN will tell you what is supposed to be there, casting numbers and such will tell you exactly what it is. The first letter on the VIN is the engine code. C= 292, D, E and F = are all 312 codes of various HP and configuration. E = 2 4bbl, F = supercharger.
Casting #'s can be either by the dist. mounting hole or over the oil filter depending on what year engine you have. Go to Mummerts ford-y-block.com web site to decipher the casting #'s. A lot of good y-block info there. Also check out Y-blocksforever.com