So, last week I went up to visit a friend and finally did the work. My buddy was a GM guy, so there were a bunch of little things that surprised him along the way and caused the project to drag out over multiple days, but overall it went off with only minor hitches.
Just before we got down to it. We started at the front, knowing it was supposed to be the simpler swap.
The absolute obnoxious spacer on the wheels originally, to allow the car's 19" Mustang GT wheels to mount properly. These things ate wheel bearings for breakfast. The silver bit at the top is the 1/8" spacer I'm replacing the originals with, for scale.
New rotors vs. old: the front.
New rotors vs. old: the front.
And the rears.
Came together nicely. The Doctor Diff front kit was very nice to work with: everything you needed in one go. Amusingly, the most difficult part was that it came with a pin but none of its parts had a hole that could fit it. We spent over half an hour trying to figure out where to cram this thing--it showed on the website photos too, so we knew it wasn't an accidental inclusion--before I figured out that the hole is created when you push the bracket and calipers together: each has a half-channel, that combined makes the pin hole.
The only real annoying part were the stainless steel brake lines. The clip on one shattered as soon as I took it out of the package. They are also doing a bit of rubbing that I don't know how to deal with (more on that below). Hopefully they can point me to a replacement, or send me one. In the short term we just eased the bracket in there without all its clip.
I'd had to get smaller tires because the 19" wheels plus the tires were creating rubbing issues. I've since rebuilt the front suspension, done some work on the rear (including the Cobra spring isolators), and now finished this hub swap, so I'm kind of curious if the original tires would work now (they were 245/45/19s). But from what I gathered asking in other threads they would have always been an issue and were pretty worn besides and so I turfed them. In any case, I miss the fuller look they gave. I think in the future I'll drop the wheels to 18s and use the space gained to add new tires with more sidewall so that there's a better sense of balance visually. Still, I'd mostly rather work on mechanics than cosmetics, so new wheels and tires will have to wait until I run these new Quiettrack tires down.
Overall impressions? Handling is a lot better with those bloody spacers gone: I use to have a low-speed wheel shimmy as if my alignment was bad, and the first thing I noticed when I got behind the wheel was not the better brakes but that the shimmy had gone. Also, there's a definite gain from just knowing that I can make more aggressive cornering again (well, at least as aggressive as the current suspension allows): previously I'd been absolutely babying it because the last shop I was at warned me that, with the old giant spacers, I wanted to avoid any undue stresses or even the brand-new bearings they had just put in would be gone again in no time.
Despite the bigger numbers with all the Cobra brake components, I honestly can't say I'm noticing any real difference in braking. I haven't really stomped on it yet, but for average everyday driving all I'm really seeing is more pedal travel required to get the same result (a result of the larger pistons, I assume). No issues, but not the transformation I was expecting.
I also have some grinding noise coming from the front now when I put her full over to the right while reversing. I'm pretty sure it's one of the steel brake lines rubbing, but securing them is not as easy as it might sound, since there's only so much line and all sorts of moving parts in there. I'll need to figure something out, but for the vast bulk of driving I haven't had an issue.
I'd say the only trouble spot in the whole process came from when my friend accidentally ground too much off one of the rear caliper brackets to make room for the Cobra rotor, exposing the channel at one end beneath the metal that a pin travels back and forth in (fortunately it's a cheap part). Otherwise it was just a slow but steady process of measuring, constant spraying with Brake Clean, and wrenching away.
Just wanted to extend a warm thanks to all that offered information and advice as I kept pleading for help. I'm delighted to have it all done, and made some last updates to my opening post to take into account what I learned. As a bonus, I think it's the now the most thorough one-stop hub swap guide on the net.
Next stage: the rear suspension. Oh man this is going to be a big one....