I'd love to see a narrow strip of black as first border (maybe 1 inch at the most). I do that to a lot of my quilts - it makes a strong frame effect. Then for the last border I'd find a print that "reads" solid dark gray. That outer print would give it some texture with the print but read solid. Maybe a print that has a bit of movement in the pattern The binding would be either the black or dark grey fabric. You still want the cars to be the "main event" that your eyes go to.
Good luck. Please post a picture when you are done. We'd love to see it.