Since you are adding non-stock SS angle strips, I wouldn't worry about originality as to how the strips are attached, and I would bolt them on using SS clutch head bolts (because they are so danged cool). One or two of the fender-to-bed bolts already go through the angle strips, reducing the number of new bolts needed. And while you are at it, why not use the SS clutch heads for the bed front-to-bedside bolts.
Spot welding SS leaves a nasty, hard-to-buff-out stain.
One other advantage about bolting the angle strips vs welding them, is that you can adjust them perfectly to fit the bed wood. Welding them in place only gives you one shot to be right.
Carl
