43 Tex. Admin. Code § 217.51 - Change of Classification: Trucks and Truck-Tractors
When a truck is converted into a truck-tractor and the registration classification is changed from "truck" to "combination," an exchange of license plates is required; however, if a truck-tractor is converted into a truck and the registration classification is changed from "combination" to "truck" the license plates shall not be exchanged, unless the change involves a major permanent reconstruction change, such as when the frame of a truck-tractor is altered to accommodate the installation of a different type bed or body. In this instance, the owner must exchange license plates and file an application for corrected title. Under no circumstances will a refund in registration fees be authorized when a combination plate is exchanged for truck license plates as the result of a reconstruction change.
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