I pulled the motor from my truck and come to find out it is not the original one. it is a 350 10243880 and has been bored out .040. My question is this I have a tamp plate to the front left side of the motor with these numbers on it 13H6 326260......was thinking that it is a id from when it was rebuilt. if it is is there any way to find out who did it and what they did from these numbers?? Thank you

On the left side of motor

 

sorry the stamp plate is on the left side by the fly wheel...(not enough coffee yet)