625 ILCS 5/3-419

The Secretary of State is authorized to adopt and enforce such registration rules and regulations as may be deemed necessary and compatible with the public interest with respect to the change or substitution of one engine in place of another in any motor vehicle. Where a substitution or change changes the classification of a motor vehicle for registration purposes resulting in requiring the payment of a greater fee or tax, the owner shall be required to reclassify the registration and pay the higher or greater fee or tax due.