I think tis is not a better way to obtain a 5V output,
use a SMPS Switcher (LM2576T) followd by a 7805, the datasheet says that there are many other type packages which withstand a wide range of temp. By using the SMPS, u can suppress the unwanted spikes if ur using it with in a rough environments
I would not go for a switching solution and the main reason is that the inductor could pick up much noise from the environment and I do not know how this would affect the operation.
I wonder if this is an LM317 equivalent with ruggedized specs?