MIAMI BEACH, Jan. 10--The College Football Rules Committee, assailed from two sides with advice on what to do about the controversial substitution rule, settles down Monday to the business of considering what changes, if any, should be made in the 1960 code.

The substitution rule appears to be the major issue. Coaches, who favor a return to unlimited substitution, which would mean reviving the two-platoon system, have had their hopes dimmed considerably by the National Collegiate Athletic Association.

That body recommended the wishes of the coaches be ignored. The Eastern College Athletic Conference backed that stand in an informal meeting.