Now that we're in 2022, where supply chain issues are an everyday occurrence, it is likely we will get to a point where 6x115 wheels are no longer economically viable to keep running. They were only used on these Terraza/Uplander/Relay/SV6 vans, 03-09 Cadillac SRX, 04-07 CTS-V and STS, and 05-09 STS-V. No other vehicle on this planet uses them and there are no aftermarket replacements except for refurbished originals. I suppose you could get custom drilled wheels in 6x115 but at $350-$400 each and up, why would you?

WHAT ALL needs to be replaced in order to swap from 6 lug BACK to 5 lug wheels? Here's what I know so far:

Wheels of course and the tires mounted on them
Wheel bearings/hubs (from a 2005 3.5L, maybe some early 2006 3.5L models?)
Nothing else should need changed out and you'll have 4 extra lug nuts left over when done

WHAT ELSE is needed?

Do the speed sensor wiring connectors match up?
Will the 5-lug bearing/hub assemblies bolt into the 6-lug steering knuckles?
Can Danger Mouse stop Baron Greenback from launching his army of bionic attack chickens?