Data collection for the EEO-3 reports of union hiring referrals was also begun in 1966, but at present only data collected since 1998 survive. You can see a list of the annual tables from the EEO-3 dataset.
We can find only three published articles that have used these data and all three relied on published tabulations rather than the original data files. Since union hiring halls are a declining organizational form these data are not likely to have strong use in the future. They might, however, be very instructive substantively documenting union decline in the face of a changing labor force and by extension other forms of organizational decline.