Amtrak operates 10 classes of baggage capable conveyances. Five of them are Heritage classes, and the others are not. The Heritage cars can fit into NYP. The others can't.
Heritage: 71 Active
Baggage Cars: These are cars built as baggage or baggage-dorm cars for other railroads and converted to HEP and to full baggage if they were originally dorms. All but a handful (possibly only one- 1188, originally 1501, which was U.S. Army baggage-dorm 89549, built by St. Louis Car Company in 1954) are Budd built. There are 31 of these cars active, from 1132-1260. These generally have two sliding cargo doors per side and no vestibule doors.
Coach Conversion Baggage Express: These are Budd built cars originally 44 or 48 seat chair coaches from the Union Pacific, Southern Pacific, and the Atchison, Topeka & Santa Fe railroads. There are currently 22 of these cars active on the system. They have a single roll up garage-type cargo door, and a dutch-style vestibule door per side.
Coach Conversion Mail Cars: Most of these originally fell into the other coach conversion class, but a few don't. They were converted to carry mail. You'll find them on occasion. They are outwardly identical to the Coach Conversion Baggage Express cars except they say "U.S. Mail Only" on the side. Since Amtrak lost the mail contract, they are used as regular baggage cars. There are 14 such cars active.
Twilight Shoreliner Baggage Cars: I don't know if they are confined to 66/67 use anymore, but they presumably were originally. I am not sure what differentiates them, if anything. I have never seen pictures of them with specific paint or such. They are 1953 Budd baggage cars built for the Atchison, Topeka & Santa Fe. There are 2 cars active.
Piedmont Baggage Combines: There are two cars in this category, owned by the North Carolina Department of Transportation. They are 400101 Yadkin River and 400102 Haw River. They are both Ex. U.S. Army St. Louis Car Company cars. Yadkin River was an army Kitchen car, 89546, from 1953, and is labeled as a Coach/Baggage. Haw River was a Hospital car, I haven't found its number yet, and is labeled as a Combine- normally I'd assume it was a Coach/Bag, but I'm not sure.
Non-Heritage: 87
Ex-F40 "Cabbage" cab-baggage vehicles: Can you call this a car? I dunno. Anyway, they are F40 shells with their engines removed, used as cab cars, with space for baggage to go where the prime mover used to be. They were, of course, built by General Motor's Electro-Motive Division. They can't fit into NYP, and there are 22 of them active (90200-90413)
Superliner I Coach/Baggage cars: These were built by Pullman-Standard, Like all Superliners, they do not fit into NYP, and there are 42 of them active. They seem to be often used redundantly on Superliners that already have a baggage car, why I do not know.
California Car Coach/Baggage cars: These were built by Morrison-Knudson for Amtrak California service, and are not owned by Amtrak- they are owned by the State of California. Regardless, there are 6 of them active in the system.
Pacific Surfliner Cab/Coach/Baggage cars: These were built by Alstom. Some were given to other California service, and some are for Surfliner service. 12 of them operate in Surfliner service, and 5 in other California service. A total of 17 of them are active.
Now then, I think quite a bit of Superliner baggage service could be met with Superliner Coach/Baggage cars (possibly more than one per train). Currently, the City of New Orleans (3), Texas Eagle (4), and Empire Builder (6) are generally required, which leaves 29 availible, and they could easily cover the Sunset Limited and Capitol Limited. But whatever.