I first read about him in Detective Comics #445 (February-March 1975), back when DC was reprinting a lot of their older material.
To be continued . . .
Now, this story was a reprint that originally appeared back in 1950, but back then it didn't feature "Marty Moran".
Big Town was actually a radio program in the U.S. that began airing back in the late 1930s, and before it ended it's run on radio in 1952, it was also a television program that ran for several years. The DC comic book based on the radio & TV show lasted for 50 issues.
Why the reprinted story made so many changes from how it originally ran, I don't know. I can only guess that even though the TV show hadn't aired new episodes in well over a decade at that time, there were still issues with the licensing agreement regarding the names involved (but probably not with the story itself nor the artwork).