Source: 1999 FORD B700 SCHOOL BUS

A Thomas Conventional on the Ford B-Series chassis and cowl that was built atop one of the last Ford B-Series chassis and cowls that Thomas had in their pool of chassis awaiting their bodies to be installed on them, as Ford had just exited the Medium and Heavy-Duty Truck and School Bus chassis and cowl market at this time, had sold their Medium & Heavy-Duty Truck division to Daimler/Freightliner to become Sterling, Freightliner had just introduced their own FS-65 chassis and cowl; and Ford and Daimler/Freightliner had entered into an agreement where Ford may not produce anymore Medium and Heavy-Duty Trucks and School Bus chassis and cowls at this time for a certain amount of years.

As of the time of writing this post, that agreement has since expired.