The one with the thunderbird valve covers might be an early block if it has 2 bolt motor mounts vs the later four bolt if original. Check for the date code on the blocks. It's below the
oil filter adapter mounting pad and is a number/letter/number(s) sequence. As mentioned look for the casting numbers on the blocks. Fords early blocks (60-64) were pretty good for casting numbers. They did not repeat on different blocks like some of the later numbers.