Help to ID very Strange 426 Wedge Block

I had a 413 like that from a '73 D600 dump truck. It was an "almost" race block with standard main webbing. The p/n was stamped in yellow pain on the side of the oil pan rail IIRC. At the time I figured it was a warranty block from after 440 production was cancelled. It was never sonic tested under my ownership because by then I was into low deck stuff.

I'll have to.check my 73 D600 hoe truck. It has it's original 413-2.

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