I don't think I would use spacers on the bottom 4 bolts. That would lessen the clamping force. They should just sandwich the metal of the cross-sill and the stake pocket. The one on the rear just above the two bottom ones should also just got thru the tailgate hinge lower bolt, the stake pocket and the cross sill. That one is going to provide the most support to keep the bed sides from spreading.
The other option (and best in my opinion) would be to clean paint off the area where the weld go, run a weld bead and touch up the paint there.


Kevin
1951 Chevy 3100 work truck
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1929 Ford pickup restored from the ground up. | 1929 Ford Special Coupe (First car)
Busting rust since the mid-60's
If you're smart enough to take it apart, you darn well better be smart enough to put it back together.