I have been restoring a 1997 E-350 Club Wagon van with the 7.3 and it's a Southern truck so rust isn't too bad but there's a fair amount of surface rust on much of the undercarriage from spending time near the Gulf Coast. The oil pan has some rust behind the crossmember that doesn't look too bad but I'd like to do something about it before it becomes a serious problem that requires removing the engine, as that's an even harder task in a van. I was thinking I should "floss" with some Emory cloth or even try to shoot a sandblaster into that crevice between the pan and crossmember and then pressure wash it, hit it with Ospho, and then fog that gap from every angle with a ton of Rustoleum. It definitely won't look pretty, but should that keep the rust at bay for several more years? I'm planning to keep this van for life, but I'm hoping to not have to remove this motor for several more years.

 

If I were you, I would just saturate the area with fluid film every 6 months. Greetings from the rust belt!

 

Mostly surface rust? Your approach sounds good, but I would skip sandblasting and pressure washing. Don't take the chance of blowing through the pan, and water on less-than-pristine metal takes forever to dry before you can topcoat. Sand, some kind of conversion coating, rattle-can topcoat. When that's dry, and anything around it is topcoated, then Fluid Film. Prepping a gunky surface that already has Fluid Film, something of a pain.