You want a NAD/PTC hybrid? I realize this could be a bit difficult at the moment, but if you ride the Screechin' Eagle at Americana, that train has a NAD chassis, but the seats and body panels and lap bars off of the Elitch Gardens (I) Wildcat, so it looks like a PTC train.
Getting back to Geauga...I remember some years ago there was a little nameplate on one of the trains (the yellow one, I think...) indicating the name of the park staffer who had built it. I think it was a matter of all new wood and upholstery, but the old NAD wheel carriers, lap bar assemblies, and other mechanical parts. By "some years ago" I mean pre-Premier, but still in the past decade. :)
--Dave Althoff, Jr.