I bought the FA-2 A-B-A configuration from American Models, with powered A-units and a non-powered (dummy) B-unit (all for DC, scale). That actual combination was not listed on their web site, but a quick e-mail to American Models confirmed that it was an option and that they had them in stock. Even though the B-unit is a "dummy", it comes with trucks that have the same power pick-up as the A-unit, however, it does not have the motor, shaft, and several of the gears inside the truck gear box. Since I ordered the "scale" version, the typical A.F. couplers were not included. The shipping box did include six Kadee "S-scale" couplers. These have to be installed.
(external link: American Models)
My units suffered some damage during shipping, which was FedEx' fault, but they were also badly packaged in the box (no buffer other than a couple of wadded-up newspaper pages). American Models did eventually send me replacement parts to my satisfaction (but that did take some time, and several prompting e-mails, including photos). The other thing I have noticed about these models is that they waddle like a duck really noticeably (see one of my articles about how I fixed that). The models seem to be quite accurate. The grills look like you can look right into the engines and see the internal structure, and the fan blades on the top are "visible". However, from inside the shell it is solid plastic. Very impressive. The two road numbers, PRR #9624 and #9628, are accurate numbers. The PRR received those units in November 1951 and December 1951, respectively. The paint job is fairly accurate, with the only glaring error being the location of the engine number; for the FA-2 they should be centered under the front windshield pillar; where they are on the model is where the FA-1 had their engine number. What is missing on these engines are the typical add-on details, such as grab irons, windshield wipers, etc. However, that is why American Models can sell these models for a reasonable price. Of course, the typical Pennsylvania Railroad trainphone antennas will need to be added as well later on. The horns are just press-fit in the shell and fall out quite easily. Most of the windshields fall off of the model very easily. A little bit of "canopy" glue fixes that problem. Apparently one of my A-units had the "low" gearing and the other the "high" gearing. Don't ask me why! They ran at wildly different speeds.
Here's my critical review with regard to the model's dimensions of the FA-2 unit (source). As you can see, the model is very accurate. All dimensions are scale:
Pilot-to-Pilot Distance: 51'-9.5" (prototype), 52'-0" (model) = 2.5" too long.
Bolster Distance: 29'-2" (prototype), 29'-1" (model) = 1" too short.
Wheelbase: 9'-4" (prototype), 9'-2" (model) = 2" too short.
Cab Width: 10'-6.5" (prototype), 10'-0" (model) = 6.5" too narrow.
Cab Height: 14'-0" (prototype), 14'-0" (model) = dead-on.
Wheel Diameter: 40" (prototype), 40" (model) = dead-on.