I’ve been chasing my tail for a few days, but I think I can now declare victory. Made the first shim out of .016” brass plate along with a few thinner aluminum shims for the side bolts, but that turned out to be a bit too thick, and the parallelism numbers were still beyond spec.
I bought some .010” soft aluminum this morning and made another shim to go across the top two bolts and that looks to be the magic formula.
Reading across the www, specs are all over the place from .002” to .010”, so I finally found a Ford Racing specific document that says runout should be within .010” and concentricity within .015”.
My runout (parallelism) measures within .010” and concentricity is within .005”…

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https://performanceparts.ford.com/downl ... g_Tech.pdf[/url]