Goofy update. I replaced the control arm bushings on the right side of my K1500 last fall. The right side had the normal eccentrics but the knockouts were still in place. We had early winter that dragged on forever. I just got to doing the upper control arm bushings on the left side. The left side had a single eccentric on the front of the front bushing, and on the rear of the rear bushing, WELDED IN PLACE, with a round hole in the middle, for a round through-bolt--not a flat-sided bolt like you'd normally see with eccentrics.My '88 K1500, and my '97 K2500 both have cam bolts, and both have NOT had the knock-outs removed. Same goes for the '94 K1500 I robbed front suspension parts from to repair my '88.
Far as I'm concerned, the presence of cam bolts indicates NOTHING.
The "knockouts" were gone on the left side, still in place on the right side. But still no actual adjustability due to the welded eccentrics.
Go figure. I bought the truck with 170,000 miles on it, no telling what was "factory" and what got "repaired" later.