imported post
To the best of my knowledge, long guns are virtually unregulated in Indiana. It's handguns that are licensed for carry, etc. Obviously, there are age and paperwork restrictions on the purchase, and the same laws of don't be a tool with it and be a danger to those around you apply, but loaded, unloaded, the long gun can be in your truck's rear window.
Now, there's a question of, "Is it smart to keep a long gun where it can be seen in my automobile?" The answer to that is most likely no, as it'll just make your vehicle a target for smash and grab skels. If that firearm is maintained loaded, all the worse.
Now, there are automotive gun racks that are lockable so that there's no way, short of the key or a blowtorch that the firearm can be liberated from the automobile, but the view of it would still make your vehicle a more tempting target in general.