I use an automotive type grinder/buffer with a buffing pad on it and a paste
buffing compound to clean up cast iron tables. I apply 3 or 4 coats of a
good paste wax and buff each coat out. RM~

PS, I also have a ryobi made craftsman contractor type saw with cast iron
tables from about the same year as yours. It also has a cast iron wing set
up for a router. Sears and Ryobi split the sheets soon after that saw was
produced. It's been a great saw and I have never seen one like it branded
with the ryobi name nor have I ever seen a ryobi with a cast iron table,
belt drive and etc.