All of the old marriage license, certificate, and application info is at the Johnson County Museum. Be sure to ask for a copy of the application. When I got mine in 1971 (which is now at museum!!!) the application had so much information on it especially about parents, place of birth, prior marriages, children of prior marriages, etc.
The address is: Johnson County Museum, Genealogy Division, 135 N Main Street, Franklin IN 46131. The ladies there (paid and volunteers) are excellent. There may be a small fee but they are so good it is worth it.