The hole at bottom of timing cover is for a cam sensor. If it is not open, it is just a pre-cam sensor cover with the boss, but not drilled. Kind of like pre-roller 80's SBC blocks. They have the provisions for the lifter spider, dog bones (flat lifter tops), and drilled holes for the cam thrust plate, but still a flat tappet cam. If the holes are not open, then no need to worry.