340 piston I'd question

nutz said
3751841 cast into crank
I belive that means CAST

According to this site mopar casting numbers

Take it for what it’s worth, by that number it’s an 80s 318 cast crankshaft.. same stroke as a 340 obviously. I compared the numbers on my 71 340 and it came up as a 68-72 forged steel.