Bump steer mods-differences in years?

[silicone boy]

My suspension is out for a total makeover right now, and I figured that I would take out the crossmember to do the bumpsteer modification as seen in the JTR manual--I have never had this problem in the car, I just figured it would be a convenient time to do it. It's kind of a backwards way to do it because the engine is still in the car--the car is on blocks and the engine is now hanging from an engine hoist. I started to make my marks (3/4 inches higher and 1/4 inch outwards) as suggested by the JTR manual. That would have put the holes really close to to top of the crossmember. Much to my surprise, my original hole location was higher than what was shown in the JTR picture. There wasn't any evidence that the modification had already been done (no extra holes). My question is, was there any variation in the lower control arm mounting point in the various Z years? Mine is a 77 280, and as I said, I have never noticed any bumpsteer, and you would surely notice it on frost-damaged Colorado roads. I was only doing the modification because it's a convenient time to do it. In any case, I think I'll leave my crossmember alone.