From what I am told by old-timer Match shooters, the more lugs on the receiver, the longer the bedding in the stock will last.
There may be some slight accuracy gains, but you will need to be a very good shot indeed to notice such improvement.

Since the M1A is obsolete for Match competition, ans since additional lugs add significantly to the cost of the rifle, not to mention the complexity of a stock bedding job, I would suggest buying a good fiberglass or synthetic stock, maybe bedding that, and call it a day.  Buy some ammo with the money you've saved.