Kilgannon/Kilgallon and Neaslis

My Great Grandfather Michael was born 1819 in St Johns Sligo to parents John Kilgannon/Kilgallon and Catherine Nealis given Michaels birth year his parents could have been born any where from 20 to 45 years pre 1819. Given that my was named  Michael its a guess if he was a first son or not. It is more on his parents that I'm seeking and being in Australia I do not know if any Thing on his parents can be found. Also I have the same brickwall on Michaels wife parents Hugh McCran and Elizabeth O'Gara who are from Ballysadare/Kilvarnet Sligo. If any one has information where to next look would be most helpfull to me.

Wendy KILGALLON