Projects Help on a fender fastener my 64 Fairlane

I took it apart about 5 years ago, finally going back together I cant remember what kind of fastener went in this top hole,I cant seem to get any access from behind to put a nut and bolt.Anyone familiar with this?
Thanks ahead for any help,,,jim

 

5/16 J nut it wraps around so you can put a bolt in it. same as mustangs and falcons.

 

Thanks Red,,,I just found it at C&G, they call it a "fender to side of cowl bolt"listed right next to the Jnut...thanks again jim