I'll admit I have never been hot-to-trot over the Golden Spike Centennial train, even back in the day. Maybe it was because of the powder blue paint and uninspiring graphics. (IMHO)
However, for those that do like it, I would say the best bet would be for Lionel to decorate the heavyweights for GSC, being that there's no real other option.
With the addition of the AM heavyweight RPO and baggage car, the closest would be if AM reran their 85's smooth side cars, which haven't been made since the 1990's. I'm not sure if the tooling still exists or is even viable after all this time. Then there's the issue of getting them around R20 curves. And as Bill noted, AM didn't do a good job matching the Meteor's paint.