If you can get the right parts, no reason they can't be made street-legal. Our Sherman Fireflies were street-legal: tail-lights, brakes, brake lights, headlights, horn (2 of them; one made noise, other made a LOT of noise: 76.2mm of noise!). Rubber-faced tracks didn't chew up the roads unless it was really hot. Didn't need turn signals because they were built before the things became law; you used hand signals..... if you really thought that someone was going to argue with you! Seat belts, same thing: built before the law came in.
Far as the Master Weapon is concerned, hey, it's a freakin' SINGLE-SHOT. Legal just as long as you don't carry it loaded while on a public highway or fire it from a road allowance.
Go ahead: have fun!
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