[fostereast]

The early ones did not have the boss or ridge along the side to drill as a side oiler.

Center oiler is a good motor. Value of a sideoiler over a center oiler is the wow factor once it is built, IMHO, I would strongly suggest not going to the trouble to drill a centeroiler to a sideoiler, it's not cheap and in general offer no benefits, unless it's a racing motor, and even then the centeroiler won lots of races too.

If I'm not mistaken the original centeroilers did not have screw in freeze plugs. Someone can correct me on this if I am wrong