This probably old hand for many, but there is a steel line that pulls oil from the rear cam bearing journal and runs to a fitting about middle top of the lifter area of the block right behind the side plate. This line is what feeds oil to the rockers. Many 235 motors ran without an oil filter, many ran with an oil filter. No matter, this line often got gummed up on the Id of the line, sometimes to the point of clogging and no oil to the rockers. When it got partially clogged, many thought pinching the overflow would help keep oil from overflowing and keep it where it was needed. So you often find them pinched. As noted above, when gm altered the oiling in 59, all of the overflows were pinched. I don’t know that there is anything inherently harmful in running the pinched version in a pre 58 motor.
