If the car is a beater and you don't care about the possiblity of grapefruit-sized hail damage or the like, definitely transport it open. If the car is pristine and you want to keep it that way, definitely transport it closed. I used InterCity Lines from NC to CA. Cost = $1450, including all insurance. Best luck.
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NSXY
95 NSX-T, 5 sp, Red/Tan, Stock, except Dunlaptya SP9000s