Hello,His records more than likely burned in the fire of 1973.One option to try to get some information such as first/last unit etc, is to see if his enlistment and/or discharge records were recorded in the county/state where he settled down in after the war.It's good that you have his ASN.That will make it easier to search for.
Other options - if he had a military funeral, contact the funeral home and the Sexton of the cemetery where he is buried as they may have military records.
Also, if he was a member of a VFW, they may have some info.
And you might contact the VA as well.
Good Luck and maybe others will provide more ideas.