Scott-
There is no need to do what you've posted. The horizontally-opposed B&S in the 580 has the front rag joint bolted more or less directly to the flywheel...there's two 3/8" tapped holes that are the same distance apart as the holes in the rubber disc. See below parts 4 and 5:
I can't say for sure if every B&S Vanguard has the same bolt pattern, but the parts diagrams for the 1641 make it seem plausible. That interface seems to be fairly common among Briggs engines.
Assuming all of this works, he'll need one 722-3001 rubber flex disc and two 711-3001, as well as the spherical ball bushing 741-3004, and none of the stuff you're showing.