FM 3 pink 70 340 duster

I see some people replying are getting uptight here.

So to the OP, if it helps you at all;

The 1970 model year started in August of 1969. So thousands of 1970 model year engines were cast during the 1969 calendar year.

The number on the front face you posted above is the engine serial number. It was stamped when the engine final assembly was done.

Later on, it would have been mated to a car and the partial VIN that may link it to your Duster is on the passenger side of the block, down low.

Look for a flat pad, it should have 8 characters with a space after the first two.

Best of luck, enjoy the search. :-)