: will I be able to soak and steam it enough to bend it?
: or do I have to use air dried lumber only ?

I would get your soaker, steamer setup and then buy one board of the kiln dried and test it out. The word is kiln dried doesn't bend, air dried is best for boats... I always forget to ask. I'm guessing that everything I've used from my lumber yard is kiln dried. I've bent Cedar, Mahogany and Black Walnut but not Spruce. I'm betting it will bend no problem.

You're pretty close to the North Woods. You could probably get a Spruce 1x4 for testing for $10 or $20.