Tom - Both Jim Carter and Classic Parts offer reproduction battery box hole covers for your truck. There are also some used originals being offered in various eBay ads. Just do a web search for "1946 Chevy Truck battery box lid" and you can find all the ads I just did in short order.
BTW - Below is a screengrab (inverted) of a battery box cover to show how it secures into the floor board opening.
~ Dan 1951 Chevy 3 window 3100 Follow this story in the DITY Gallery "My Grandpa Carl's Truck and How it Became Mine" 1966 Chevelle (Wife's Hot Rod) | 2013 Chevy Silverado (Current daily driver) US Army MSG Retired (1977-1998) | Com Fac Maint Lead Tech Retired (1998-2021)
