I spent my weekend building crates for toting my trains to shows and meets. The inside dimensions are 24" x 20". I did one with three 24" troughs for my F3s and three with four 20" troughs for freight cars. This accommodates 40’ box cars, woodside reefers, tank cars, etc. I’ll probably build another long one at some point if I get some bigger box cars.
They stack, and there’s a shallow one for tools.