Yes. Section 393.93 of the FMCSRs (49 CFR 393.93) requires seat belts on trucks, truck tractors, and buses manufactured on or after January 1, 1965. For vehicles built on or after January 1, 1965, but before July 1, 1971, the seat belts must comply with the FMCSRs in effect on the date of manufacture.
For vehicles built on or after July 1, 1971, the seat belts must comply with the applicable National Highway Traffic Safety Administration's Federal Motor Vehicle Safety Standards concerning seat belts (49 CFR 571.208, 571.209, and 571.210).
When the FMCSRs require conformity to a Federal Motor Vehicle Safety Standard, the vehicle or equipment must conform to the version of the Standard that is in effect on the date the vehicle, or a subsequent version of the requirements.