I just finished tearing down my 88's V6 for a full rebuild despite many urging me to just go newer, and found these marks on the crank and block. Does anyone know what they mean?

Ok last section of the crank by oil pump and rear main - reads "A - 21 - 351"


On the back end of the block below rear main - reads "695 A 19"

Hey man, wish I knew enough to answer your question. I’d recommend posting this over in the Tech/General Engine section as you might get more responses over there.