on the front of the engine.
look where the water pump bolts through the timing cover to the block.
on a 351 th timing cover water pump will be about 3/4-1" below the head.
on a 302 the bolt will go in right below the head.
that looks like a good car to get i see from the pics it looks like it has power disc brakes and power steering.
if it is a 351 id bet it also has a 9"rearend as well.
good luck hope you get it.

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68 falcon sport coup 289 toploader 9\" 390\'s detroit locker
68 falcon undergoing v8 swap
67 falcon 351w auto
68 falcon fact ac
67 falcon next project no motor or trans no rot either