I'm not finding Daniel on the 1930 U.S. Census. I looked for Daniel Sullivan, born within 2 years of 1878, born in Ireland, arriving 1923-1930. I also checked Daniel's who had initials other than R (in case there could have been an error) and still did not see a likely candidate. I did not check the actual images for Daniels who appeared to be married and who had Sullivan childen living in the household.
Last night I checked for his immigration, but I don't think it was as thorough as the above census check. I'll have another look for an immigration record.
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I'm sory, I didn't see any likely candidates on the immigration lists.