I've owned my 84 f150 6 cyl for over 2 years. Last year I all of a sudden had starting problems. A "helpful" co-worker replaced my starter, and I think the ignition switch relay. It turns out a new battery was what I needed. ;-) So.. that worked fine for a while, now all of a sudden I have the same issue. New battery(charged and tested), New starter.. It simple "clicks quickly sound" when the key is turned. Any help would be greatly appreciated!

check starter solenoid make sure it has good connection it may need to be replaced

Check all cables for corrision,including at the starter.