you can see the ridge at the top of the cylinders. #5 and #7 look like scuffs or water erosion at the top of the cylinders. if this engine was run on a dirt track without very good air filtration i'd think the dust would grind the cylinders up. there also was a deal back in the '70's were chrysler bought a bunch of inferior cast iron and used it. could be a soft block,...? i've ran and beat the snot out of hypers without wear issues, but i put them in just as the literature said to do. i think the block is just plum wore out.

i did a 360 for a friend some time back and the block had over 100,000 miles on it. the oil was changed frequently and the engine was just a driver. it only had about .001" of taper, no ridge, wear marks or nothing; i think it was a '90's block.