I’ll see your 1977 law and raise you a 1972 law from that link you posted :
NOTICE THIS PART
“REQUIRED SSA TO ISSUE SSNs TO .... AND TO ANYONE RECEIVING OR APPLYING FOR ANY BENEFIT PAID FOR BY FEDERAL FUNDS”
1972 Social Security Amendments of 1972 (P.L. 92-603):
Required SSA to issue SSNs to all legally admitted aliens at entry and to anyone receiving or applying for any benefit paid for by Federal funds; Required SSA to obtain evidence to establish age,citizenship,or alien status and identity. Authorized SSA to enumerate children below school age at the request of parents and at the time they first entered school.
1972 Social Security Amendments of 1972 (P.L. 92-603):
Required SSA to issue SSNs to all legally admitted aliens at entry and to anyone receiving or applying for any benefit paid for by Federal funds; Required SSA to obtain evidence to establish age,citizenship,or alien status and identity.
Yes, it required SSA to issue an SSN. It did not require a welfare recipient to obtain a SSN until 1977. The citizenship, alien status, age are found in the NUMIDENT file after the SSN is applied for.