Addressing some rust starting in my truck bed

[Dead Parrot]

Start soaking those front bed bolt nuts in penetrating oil. Several applications over several days. Easier to clean and restore the bolts and holes with the bolts out. Give the oil several days to work as you don't want to wallow out the square holes the bolts sit in. If by yourself, set a heavy weight on the bolt head to keep it from rising up and turning while removing the nuts.

I think there should be one or more drain slots on the front to let water out. Often plug up so the water just sits there. If water sits there for days, rust will happen. One option is to drill a hole at each corner.

Make sure there isn't dust/dirt/salt trapped on the underside, especially on the back end.

Doesn't look too bad. Might get lucky and it cleans up nice with some wire brushing.