Did a 1994 Ford F-150 come out with 306 6-cylinder motor?

No, Ford did not offer a 306 cubic inch (5.0 liter) six-cylinder engine in the 1994 F-150. The 306 was a V8. The 1994 F-150 had inline six-cylinder engines, but they were smaller displacements (e.g., a 4.9L).