I have examples of Superliner Is in HO and N by Concor of which I can't vouch on their accuracy as well as the K-Line and Williams Superliners in O. The Williams are not terrible if you replace the trucks, pull out the silhouette window inserts and put in an actual interior. I started to replace the trucks on one and that's about as far as I got, but of course I only have access to Superliner II trucks and the Williams, while not really a Superliner I or II are painted for Phase II and Phase III so they should have Superliner I trucks.
Correct me if I am wrong, but as I recall, Superliner IIs were delivered in Phase IV paint and were the first cars to wear this scheme in 1991 when they started to arrive.
As for the P42s, we can probably figure out the nose. If it is just a headlight variation that isn't very difficult. The venting for the P32AC-DMs is pretty easy with a slide tool.
