Where's the 340 crate engines???

Hi, my name is Riley and im really new to all this... but i seen this post and i was really hoping that there are people still following this thread. My father-in-law died this past year and my wife and I finally started to clean out his house. When we started in the garage i noticed his Plymouth Duster he built. Well when we went to pull it out i noticed a what i thought was just a bunch of plastic in the corner but to my suprise there was a motor that appears to be new. He had purchased it online and had it shipped to the house. Im not sure if it was crated or rebuilt? But its just a case with heads on it. When i read the stamp i had never noticed the numbers. It appeared to be a 340???? I just need some help trying to figure out what exactly it is and what its worth? All i know is its bolted to a board thats on wheels still and just sitting in the corner... its got light rust on the case but the heads and valves appear to still be lightly oiled and rust free still? I added a pic of the numbers if anyone can please help me figure it out! Im completely lost to what i have here

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thats a 340. have any more pics of thr short block and heads?