MN42630035319
MN= Plant identifier for the Marysville engine plant
426= Displacement
3003= Build date October 17, 1969
53193= Sequence number
there's a fifth digit to the sequence number for 1970 model year & it is/was a
hemi'cuda 
So the 3 after the sequence number means 'Cuda? I did not know that. I've never seen any info on decoding the sequence numbers.
The sequence number has nothing to do with what car it went into.
The VIN on the block told them it went into a cuda. Serial numbers were issued in groups or blocks so if you know the group range you can surmise what type of car it went into.
