1557 and/or 1648: rider gons. Capacity depends on who's showered and how well you know the person next to you. Let's round it off to "lots." One of these gons is out of service, the other is used as a standby (9613 and 9615 perform daily duty).
0306: has eight wicker chairs on the ground floor, and four cupola seats upstairs. When used as a caboose charter we allow 12; when used as parlour space we sell eight seats.
05635: was listed as seating 10, but it's out of service (interior is pretty beat up, and an inspection has revealed some sill problems).
5510: a stock car fitted with a center bench seat. Since it hasn't been rendered serviceable, I don't think anyone's counted.
JAC