Gene, I may be embarrassed by a fuzzy memory of exactly what I did about 40 years ago. But looking at some pictures taken during my more recent rebuild helps a bit.
Because the antidive mod involved tilting the upper A-arm lower on its rear-facing side, the lip on the inside -- that open area that straddles the vertical U-section that mounts the pivot rod (if that makes sense) -- would contact that vertical support when the suspension went into droop. You'll recall that the side of the vertical "U" becomes wider toward its base. I ground away some, but nowhere near all, of that reinforcing inside lip of the A-arm to gain the clearance I needed. To the best of my memory, the interference occurred only on the rear inside opening since its lower mounting placed it nearer a wider portion of the "U." I believe that if you do not tilt the upper A-arm toward the rear, you will not encounter interference. And, as you point out, you can always return to the original configuration (if you don't mind painstaking realignments).
As for the binding, there was none with the original upper balljoints. But hand-turning the spindles revealed binding with the new balljoints, and they were oriented correctly in the A-arms. So I eliminated the A-arm tilt while in the process of reassembly.
Be aware that lowering the upper A-arm pivot results in (more) negative camber, all else being equal. Since you remove shims to adjust toward positive camber, you may not be able to get back to where you were. Each car is a little different. In my experience, however, 1 to 1.5 degrees negative does not wear the front tires unevenly, given somewhat aggressive driving.
I was happy with the mod and felt that it increased front bite, which -- as you know -- the car needed. I was running widened steel wheels (very few aftermarket wheels available for the Tiger's bolt pattern in those days, and none with acceptable offset), fat street tires, cut-down CAT springs, 7/8" front bar, 5/8" Addco rear bar, 1" rear lowering blocks, "heavy duty" Monroe shocks (still can't afford Konis), welded-on traction bars, and a single spring clamp near the front of the right rear spring that eliminated axle tramp.
Today I'm amazed at how much punishment the front suspension took. I broke an upper front shock mount once, but nothing else failed. When I rebuilt the front suspension a couple of years ago, magnaflux revealed a crack in one of the lower pivot pins. I replaced them both.
I don't know which Rootes sedan the spindles came from. My son also owns a Tiger, and a friend of his who is restoring an Alpine came up with three sets.
Your Tiger is much more modified than mine ever was. I am surprised that the Midget rack and MGB steering arms have not produced the advertised benefits.
It's probably not possible to compare my experience with anyone's these days. So much more is available for Tigers, and today's DOT "race" tires are phenomenal.
Now that I've gotten old and my Tiger is driven much more gently, none of my mods are even remotely needed. But it was fun at the time.