I had a '40 pickup many years ago. I don't remember where the battery was. I thought yours be be like the ADs under the floor on the passenger side close to the starter. The access door has a loop handle that you turn to latch and un latch and it comes completely out. I'm going to use one of them on my '26 roadster.

"I wonder if God created man because he was disappointed in the monkey?" Mark Twain