@ MTLJoe - Is this a modeling question or an (MTL) manufacturing question? If the latter, then assuming you aren't going to tool a suburban coach, I'd go with CNJ lettering on the single window coach. But if a modeling question-
The easiest way to approximate it would be to take a MTL single window coach and cut out a 2-window section. That might leave it a scale foot too long, but the appearance would be very close. My recollection from my HO days 50 years ago is that the Athearn coach out of the box is pretty close, at least in length. Maybe get out the shrink ray?
One difficulty in passenger car modeling is the confusion over car length caused, to a degree, by how the railroads themselves denoted car length. For instance, a 78' coach on many railroads is the exact same length as a 70' coach on the AT&SF- because AT&SF measured the inside length of the passenger compartment WITHOUT diaphragms (70'), while the other railroad might measure the car over the diaphragms (78'). Even worse, you might assume that an ATSF 70' coach and 70' baggage car were the same size, but no. Since the baggage car had no diaphragms, it is about 6' shorter.
The Atlas coach is 11' too short (60' over diaphragms vs 63' interior dimension PLUS 2 diaphragms, or about 71' overall). The 60' overall length car done by Atlas (and Bachmann before them, the Bachmann scaling more like 58') was almost specific to the Chicago & Northwestern. For a longer paired window car, you could lengthen the Atlas by adding one or two window sections, to get closer to paired window suburban cars. There might also be a way to utilize their observation but chopping 2 of them to yield a single window car, but I don't have one to examine. The issue with the Atlas is that with the one piece casting, it can be difficult to get the seams where you want them on both the side and the roof,
Perhaps more common at a similar length were the PRR P-54, which ended up on several PRR subsidiaries, and a few were sold (used) to the Chicago and Western Indiana (before they picked up used Erie Stillwells).
The common 68-72' length suburban coach is unfortunately something unavailable in N scale out of the box (AFAIK), but can often be approximated by chopping a section out of a single or paired window coach as appropriate.
