Wheel and wheel spacer advice

I bought a set of Coddington Smoothies awhile ago. After the addition of a cobra brake upgrade the wheels will not fit. I have not had the tires mounted on the wheels yet, and can return them to discount tire direct for a full refund or exchange. They don't make Coddington Smoothies for the cobra. Should I return the wheels, or add a spacer and go with what I got.
I don't want to take the brake kit off.

I guess I will try like a 1/4 or an 1/8th and see what happens. I am just very hesitant about using them. I guess that should mean something. Thanks .