I've never seen a manufacturers part number listed for tires, just the model of the tire, and then the size .
On your rear tire, don't get a 120 width rear tire, that seems to be a common problem with ordering tires for our R65's, the correct size, is 4.00x18, not a 120x18 .
The 120 will work, but it is a real hassle to get the rear wheel on and off .
This tire dealer, usually has some good deals on tires, and if you purchase two tires, shipping is free .
www.swmototires.com