I've noticed what seems to be a slight knocking sound while I'm driving. This mainly occurs when accelerating between 45-55 mph. I don't hear it while cruising. Does this sound like it could be spark knock, and if so what are some things I can do to get rid of it.

Btw the truck is a 1989 F-150 with a 5.0L V8 and 79,000 miles on it.

 

Higher octane gas... retard the timing.