Here's a suggestion:
Go to General Truck Talk (most frequented sub-forum) and post with the Subject "Anyone here have a '39 Chevy truck?" Then in the body of the post just say you're having a hard time finding out what goes in that hole.
Chances are very good that you'll get your answer there.
The problem with your question is that it technically could go in no less than three sub-forums - Interiors, Pant and Body, and Doors, none of which get anywhere near the amount of traffic as the General Truck Talk sub-forum.
Good luck.
