Charrlie_S said

Not enough info, and or pictures. There is a difference in the crank pocket/converter nub/input shaft between 1967 and 1968. If the years of the engines/trans are really as stated, that should not be the problem. There is also a difference between the 904 and 727 converters. With the vehicles listed, they should both be 904 units.
What is the exact problem? You mention the converters having differences. I can't tell by the pictures. What do you see as being different?
Also as stated it is possible the converter was not fully seated in the trans

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