UPDATE:
Apparently, there are only one set length of pins for these calipers, both for regular, and HD brakes, up the 8400 GVW- FYI...
I called the guy at Mcgaughy's, he was helpful enough, and basically told me I was an idiot, or, at least, made me feel like one...(in a nice way), he'd never heard of problems with their spindles...they should be considered "oem" replacements. All stock hardware should work fine.
Great.
I am learning...
Looks like the original set of rebuilt HD calipers I bought may have had the steel sleeve inserts set a bit too long. (The shoulder on the bolt was bottoming out on the sleeve end before it went into the backside of the caliper.) I bought a set of Wagner "loaded" calipers, (they come with EVERYTHING), and looks like it will work since the steel insets are more "flush" to the caliper housing... but we'll see...
The drop on the truck looks cool so far, BTW...2.5" in the front with Mcgaughy's Spindles, and 4" in the rear with their shackle relocator kit...but I'm thinking a bit lower might be in order..hmm...so many options...