Your options are wide open as to what horns to put. As for legal issues, that is a state legal issue, each state will be different. Your 14 Tacoma has an OE air horn ? interesting. You can replace the OE horn with anything you like. The more you are willing to spend, the better or louder the horn. We have a few people around here who have a freight train horn on there trucks. They are very loud. Maybe to loud. It is a distraction for other drivers. My 04 4 Runner has the OE electric horns. I find them to be plenty loud with a good tone. If you do an electric horn, you need to make sure that the horns are powered through a relay. A horn takes a lot of supply power. If you want to save some money, you could always take a trip to the salvage yard, and pull a set of horns off of something there. My 97 Chevy Silverado has a set of horns from a Cadillac SRX. One of my horns went out so after a trip to the salvage yard, that was a good replacement. I tried a cheep air horn, but it sounded like a cheep horn. The Cadillac horns sound much better. Be sure if you get some from a salvage yard, that you get both horns. Horns are tuned together for a proper pitch.