Hope you have made progress with your ancestors. This is maybe in the wrong era, etc. but I couldn't help but notice that at least 3 of your surnames, Mahoney, Herlehy/ Hurley, and Kelliher, are found in a set of parish records that I am working on, for the RC parish of Inchigeelagh, in western Co. Cork. The IGI Batch Numbers for that parish do represent the transcriptions from the Casey Collection. If you go into LDS Family Search online, and go to the IGI, just put in C700791 for baptisms, or M700791 for marriages, (be sure to capitalize the letters or it won't work) plus British Isles, then Ireland, skip the rest, & start putting in surnames, etc.
If you don't get this, e-mail me and I'll send you some websites that do a better job of explaining that strategy.