IH stamp on 318 block

There was a brief period in time where I was messing with a lot of small block fords (fox body mustangs). I remember that every 302 I tore down had a massive ridge at the top of the bores. The iron they used was like butter compared to mopar blocks.
That IH block could possibly be from some farm equipment. I used to work at an Allis Chalmers dealer and saw quite a few slant six's in combines. Cant say I ever saw a 318 in anything except for boats. They were very common in boats.
More than likely mopar farmed out the work to IH's foundry to keep up with production. Anyways, thats a cool block. Anyone else ever seen one of these?