I have a inline 300, and I am trying to determine what these numbers mean. I found them above the starter on the block. ( E1T6E6015AA )

I have never messed with a 300 before. But the mains or rod bearings are rattling a bit. My oil pressure is right at 9lbs idling. I have been doing some research and it seems that there is different cranks in these. Correct me if i am wrong. I am wanting to buy a crank kit to put in it. I appreciate all the help.

 

That is a 1981 or later block casting number.