For that rear tire, you may want to go with something like this:
Avon Side Car Triple Duty Tire - Motorcycle Superstore
Since you won't be leaning (or applying power through it), the flat profile of a sidecar tire will probably make the car feel a bit more stable through the curves and less twitchy on the highway. Better contact patch and it'll probably wear better too, as the wear and tear will be distributed across the whole width of the tire instead of just the middle.