Here are a few reference pictures showing the Moog K7103 Offset Bushing compared to the Moog K408 standard bushing.
I do not know why they manufacture the offset bushings shorter which requires you to add the plated spacer washers to make up the difference?
i don't know why either but I just installed a set in my 67 and they fit perfectly. Only thing is the directions say to point the arrow toward the ball joint. Thats incorrect. One needs to point away to get most caster
They did that because they used bushings from some other application, and are using the washer to make up the length difference. Yuck.
OP, consider a tack weld on the new bushings after installation. I did a zap to the control arm (Mig or Tig welding only, NO ARC WELDING). That way they're held in place in case the press fit on your arm is less than ideal. This is what the factory collars attempt to do, which I used and tacked them, too.