I have done it from below, to a Megablock (iron) with a patched portion lacking the dipstick hole. I took measures from an old 440 block (any B/RB) and bored straight up till the hole was some .050"-0,1" deep, to steer the drill, then you sight and use the same angle as the cylinders/pistons (45 degrees). Be careful when the drill goes through on the backside. The hardest part is to get the new dipstick in from top, in a cramped engineroom. I used an openbox wrench around the dipstick flange and hammered it down, with RTV. Good luck!!