1974 Plymouth Valiant 4-door slant six, disk brake, A/C, was a low mi driver ... complete part out

That I cannot say, but I will say this...uShip is the place to look to ship this kind of item.
Being extremely large and fairly heavy, standard shipping methods will be hundreds I am certain.
That being said, last Sunday I sold the front and rear seats (from the other 1974 Dart SE I am currently parting out) to a gentleman who lived about an hour south of Chicago. I happen to have been hauling a car to Freeport, Il. so I told him I could meet him in Chicago on my way through so long as he prepaid...and we did! Worked out great for both of us...
That being said I do travel quite a bit, however not sure when the next time I will be going to Chicago will be.
However if you are in no hurry, and pay $125 for the seat, I'll gladly bring it with me the next time I go through the area.
That is about the best I can do at the moment...