I was told after I had removed those two round headed bolts on a 216 that a mistake was made on my part because those two bolts are critical to the correct positioning of the oil pump in the block and that is why they are rounded because they are not to be removed. Luckily for me,when I replaced those 2 bolts and the oil pump, all seemed to work ok. When rebuilding my 235, I left them alone.

Drew