For '79 there are several part numbers that are required. It also depends on where the truck was built.
Stripe kit, for trucks built at other than Michigan Truck Plant, Tangerine & Gold, Regular Cab D9TZ-1020000-DE
This is for the cab forward. There is a different pn for the bed stripe kit.
Let me know if you have a short or long bed, w or w/o aux. fuel. and I can get you the p/n's you need to look for.
Also the trucks built at Detroit take a different kit (??)! Whats the 5th character of your VIN?