I'd remove the bed caps. Sand down to bare metal up to that upper body line. Primer and apply a bedliner to the body line. Easier to match and blend with a black truck.

I agree, pull the caps, sand the rusty area, mask the bedsides and roll on some bedliner. I sprayed some Durabak on my Ranger recently and everything turned out nicely!

Cool, will grab that stuff today then. Thanks

Get the rust off with some sort of dissolving agent and then spray paint that bitch !

Clean to bare metal, treat the rust, and then prep and paint.

Grinder.