[TTBlows]

when you say fill the holes, Im just thinking about planting big ass pieces of 1/4" steel plate down as much of the length inside and outside the frame rails, basically where ever I can fit it, that should work dont you think?

Do it (altho .250 is probably overkill)

 

[TTBlows]

How big are those holes? Could you just hole saw plate to the appropriate size? I'd use 3/16", that's more or less what the frame is. Then again, I'm not certain how much strength you're gonna add just filling the holes. I'd plate a couple places and call it good.

Are we aware of actual failures anyway? You might just be wasting your time

 

[TTBlows]

OTOH you guys should see the frame cracks in the '97 F350 Nathan got for parts.......numerous cracks in the rear. It was a field truck, oil & gas and those guys BEAT on those things. Also apparently they mount the utility beds straight to the frame, no bushings or anything.

It had cracked both sides where the rear shock mounts are riveted to the frame, and was starting to crack where the stop bracket for the overload leaf was mounted.

 

[TTBlows]

As I mentioned on a '97 F350 (pics posted only for amusement purposes only, I am not saying this relates to the earlier swiss cheese frames or is proof of impending failure)

Crackage at overload leaf stop:

Patchage:

More patchage: