Ford made no F-Series body changes in 1977, but did update trim, moldings and badging.
A rear window defroster was added to the trucks' options, and A/C (previously not available on 6-cylinder trucks and some V-8s) was available on all pickups.
The 360 cu.in. and 390 cu.in. V-8s were replaced with 351 cu.i. and 400 cu.in. 2-barrel engines.
Ford marketed the Free Wheelin' truck in 1977. Its unique look came from rainbow side tape stripes, a black front push bar with a space for fog lights, a blacked out grille, black tailgate lettering with orange accents, black door panels with silver and red trim and black, silver and red seat trim.
Other 1977 F-Series updates included:
- The trucks' radiator support was added to a growing list of galvanized steel parts.
- Front and rear wheel wells featured plastic splash shields.
- The front fenders, the tailgate, lower radiator reinforcement and rear cab corners were made from pre-coated metal.
- Truck undersides were coated with zinc primer.
(Excerpt taken from: http://trucks.about.com/od/fseries19731979/a/ford-trucks-1973-to-1979.htm)