Could An Old Index Help?

FamilySearch, Ancestry.com, and other sites create their own indexes to certain records. There may also be "older" or "original" indexes to these same records. The National Archives created many card indexes to certain records, particularly in 1930s and 1940s. FamilySearch has digitized some of these card indexes and put them on their website.

Passenger lists for Philadelphia are an excellent case in point where there are "new" indexes and "old" card ones:

Pennsylvania, Philadelphia Passenger List Index Cards, 1883-1948

Pennsylvania, Philadelphia Passenger Lists Index, 1800-1906

Pennsylvania, Philadelphia Passenger Lists, 1800-1882

Pennsylvania, Philadelphia Passenger Lists, 1883-1945

The first two are older indexes. The last two are newer ones.