bfj2:
When I bought my M1A new in the box, it came with a copy of Department of the Army Technical Manual ,TM 9-1005-223-12, Operator and Organizational Maintenance Manual, 7.62-MM Rifle M-14 and Rifle Bipod M2.
It is a good manual. although for the M-14, it applies to the M1A as well.
If your Dad bought it new it should have came with one. Call Springfield and they should be able to supply him with one.
Fred