Walthers / Rivarossi offers an RPO, Baggage, Utility Coach and Utility Combine that are each 60' long - just like their prototypes.
Athearn makes (if I remember right) a 63' RPO, 67' Baggage, and 72' Coach that are prototypical length. They also offer a Diner, Pullman, and Obs car that are 72' long but should really be 80'. Rivarossi/IHC also offer Baggage, RPO, Combine and Coaches that are correctly around 66-70' in length.
BTW you asked about 40' cars...the Burlington actually did have some 40' heavyweight cars they used on some branchlines.