Safety isn't an issue with an in cab tank that's in good shape. I don't think anyone has ever heard of a fuel tank blowing up or harming the occupants in anyway. If there's a collision that blows an in-cab tank (that you are just inches from), you were already dead. A tank hanging from the rear frame rails is much more apt to get hit or damaged. I don't think you could blow a fuel tank like a bomb just by hitting it any way. It survived 48 years in the cab.................
Too many urban myths,
Scott