Are you specifically not seeking the cars Lionel made (I think?) to go with them at the time?
I know they made a 4 pack and a 2 pack of cars for the NYC PA's that are of the same vintage, but I do not off the top of my head know the catalog numbers for the Santa Fe ones (if they were in fact made).
The cars that went with the NYC were (I think) 15", they were before the detailed 18" cars came out. The ones for the NYC set had the old style window silhouettes for passengers. They still go nicely with the engines.
I'm guessing maybe you are going for more a scale than toy look for the cars you will buy since you mentioned these were the Scale PA's, but figured I'd bring up the matching cars anyway. I may be able to do a catalog search later today to see about the Lionel numbers if you are interested. I imagine they were in a 1998 or 1999 at the latest catalog, since these were in the 1997 Classic catalogs (the SF PA was on the cover of one, the NYC PA was on the cover of the other).
-Dave