Integy still make some 31mm tire and rim if your looking for rubber. If it was me, I would run some Yokomo foams(32mm) and not have to worry about the clearance of the inner rim and the rear knuckle. I don't think you will have a problem since it does not have pivot ball suspension or anything that will get in the tires way. Racer Choice and Frewer make lola body for 200mm touring cars, you can purchase them from tower if your local hobby shop does not carry them.
Speedster, if you want the tire to flush with the body, get some rims that have a lot of offset, about 3mm+. Yokomo rear 31mm tires haave a lot of off set on them, you should try them.