Not sure of the offset (I guess I could figure it out

) but they are a 7.5" backspace.
If CCW could build them, you could go with a backspace of about 7-11/16" which is probably the absolute max inboard you would want to put the wheel. For flexy flier slicks I'd stick with a 7.5" backspace, maybe even a 7.25"
Yeah they are 17x12's.
Just need Kumho come out with the tire I want, and buy 2 18x12's.