I used to drill and make them removable from the front in the early 70's i also modified the front of the block to get the extra oil in the cover to drain back to the pan faster. This was easier than adding a fitting and drain line to get it back to the pan.I learned the oil drain trick from some of the old timers that raced these old engines on circle track and speed trap runs.
If you modify the block to drain the oil from your timing cover, the gears explosions will end and RPM will increase dramatically. My old 6 was built in the 70's at and has a lot of miles on it and has seen RPM's way over the normal range.
