You could get a million suggestions on your question regarding frame and chassis coatings like corrosion protection stuff. However, being a southwest truck and if your free of flaky rust and now in the southeast, then i would say a light coating of some rust protection spray. When i drove my 77 year round here in the northeast, i would soak it underneath and then some with all kinds of oily stuff. I like lanolin based fluid film, some think its junk though. It works great for me.