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It's very dificult to find true 1:48 scale diecast vehicles because 1:43 is the "standard" scale that's close to O scale. If you seach for 1:43 scale vehicles, you'll get lots of hits like this one: http://www.ashevillediecast.com/cart.php?target=category&category_id=483. As I said, 1:43, while slightly undersized for O scale, is close enough not to look obviously wrong.