In the SCTA;
If it is produced as a "Street Legal" Motorcycle, like the many Dual Sport models all the major manufacturers produce, let's say a Honda XR650L, it would be legal for the Production class. If it is a Honda CRF450X that has a light kit installed and has been licensed, as can be done in some states; no, it would not be a legal Production class bike.
Yes, a tire change would be legal as well. A wheel change could even be legal if there are no tires available for the speeds expected to run.
If you are intending to run this type of bike, be sure to contact the SCTA Motorcycle Technical guys listed in the Rule Book and let them verify that this is accurate information.
JW