There are patch panels available for both of the above-mentioned truck, and they can be GLUED into place using Norton Speedgrip.
is a Canadian distributor ... but I am sure they are available in the US as well.
Cut out around the rust holes, into the good metal ... but make sure that you leave enough (an inch or so) of overlap, smaller than the repair panel, to have something to glue to.
Sand the paint off of the work area using coarse (36 grit?) sandpaper.
(Honest, I don't work for Norton ... but they have some new "Blaze" discs with a roloc attachment that will work very nicely with your die-grinder.)
"Dry-fit" the patch panel, drill and screw it in such a way that it can be re-screwed into the same position once the glue has been applied.
Apply the glue in an "squiggly" pattern to the prepared (Sanded to bare metal, cleaned with laquer thinner and dry ) surface ... and then glue and screw it into place. That speedgrip stuff is available in a variety of working times, from 1 - 40 minutes. 5 or 15 is probably what you'll want to use here.
Don't get overly concerned about any of the glue that may have "squished out" as it is completely sandable and paintable. After the glue has cured, you can remove those screws and get to work on the rest of the operation. Go ahead and beat on this stuff. The glue is tough and flexible, and wont crack or peel away.
That sound pretty easy ... doesn't it?
The glue is pricey, ($50?) and you'll need to buy, borrow, or rent the manual applicator gun which is about $100. Sounds expensive, but it's sure a lot less than buying a mig welder. LOL
If you have some of the speedgrip product left-over, just leave the mix nozzles in place. The next time you want to do another repair ... and you will find many uses for this stuff as it works on almost anything including most plastics ... simply replace the mix nozzle with a new one and you're "good to go".
Yes, you can buy mix nozzles separately in 6-paks.
By the way ... if there are any expert body guys out there that have any opinions, corrections, or additions to this ... PLEASE feel welcome to add them. I'm a "parts guy", and this has been what I have learned by "osmosis"