Don't give up, hopefully he is alive, well and a good guy.
The internet was the final difference in our case. There was no WWW when she started. Of course she actually had some help from her Mom and you may not until she gets sick and tired of you pestering her.
There are websites dedicated to people finding people and you have some clues you can use...your date of birth, where you would have been conceived, you mom's first name and her description at the time, her occupation at the time etc.
Keep in mind that old saying though, be careful what you wish for, finding out could be worse than not knowing...I'm not being cynical...just be braced. I mean maybe he's Bill Klinton!
“I mean maybe he’s Bill Klinton!”
Gee...That’d really make lkco one in a million. lol
But seriously, lkco you will be in my prayers.