The 83 gear/drive will not fit the 80 cable. Either use the 83 cable or change to the 80 drive. Although the rim size is different, the tire in 82/83 is taller and fatter than 80/81 tires. It should be as close to the right speed reading as any Honda speedo.
if the wheels didnt come with the rotors there will be some alinment problems ....theres usealy a shim and gaskit that has to come off ....if the whell is by itself make sureall the gaskit is gone where the rotor hooks up to it