The traditional roller bearing Blomberg B is the one Athearn did such an incredible job on, and it comes with all of their F-units, GP9's, and GP35's. Proto 1000 and 2000 units thus far have a rather lame rendition of the regular Blomberg that looks pretty weak next to Athearn's. Use the Athearn as a cheap, drop-on replacement (you may need to trim the large pin that fits into the truck itself) and you'll get a 100% improvement in overall appearance. The Kato version, as found on the Atlas GP7 and Stewart F units, and the Kato GP35, isn't quite as nice as the Athearn, but it's still good. The Bachmann Spectrum GP30 and Bachmann Plus GP35 come with a very weak Blomberg; Unfortunately there's no easy way to replace it. The Atlas/E-R FP7, made by Roco, also has a cruder Blomberg than the Athearn or Kato, but it's not nearly as bad as the Bachmanns.
Everyone and their mother, it seems, has done it. Here are a few. Atlas/Kato GP7 Atlas/Roco FP7 Proto 1000 F3A Proto 2000 GP30 Stewart/Kato F3B
The AAR Type A switcher truck was used by EMD, Baldwin, Alco, Lima, and Fairbanks-Morse on various models. Pennsy engines equipped with AAR Type A trucks included Alco S-3, S-4 and T-6, Baldwin VO660, VO1000, DS-4-4-600, DS-4-4-750, DS-4-4-1000, S-8 and S-12, EMD SW, SW1, NW2, SW7, SW900, SW1200 and Fairbanks-Morse H-10-44 and H-12-44. HO scale renditions are available from Atlas, Roco (on the Walthers SW-1 and H-10-44/H-12-44), Kato (also used on some versions of the Con-Cor SW-7), Athearn, and Proto 2000. Tiger Valley Models also has Type A sideframes, sans journals, and they make the appropriate journals for you to attach.
Here's the one found on a Atlas/Roco S4.
AAR Type B road trucks
The AAR Type B road truck was available in 2 versions. One, equipped with GE traction motors, has a wheelbase of 9 feet 4 inches, while the comparable Westinghouse traction motor equipped AAR Type B has a 9 foot 10 inch wheelbase. They are equipped with roller bearings. GSC cast most of the GE traction-motored versions of this truck. Generally, the Westinghouse-motored version had 4 sets of the leaf springs, the GE, 3. However, the GE-equipped trucks under some RS-1s also had 4 sets of springs.
Both GSC and Adirondack made GE trucks; There are no known examples of Westinghouse trucks which actually bear an Adirondack logo. Older GE trucks made by GSC have the GSC logo above the inner coil spring on the left side of the frame casting, but newer GSCs seem to omit this. Some GSC trucks made for Alco have a rectangular Alco logo centered above the leaf spring set. Adirondack GE trucks have a small hole above the outer coil springs, one on each side. Older Adirondack GE trucks have the AD logo just to the left of the leaf springs, but newer ones have the logo centered above the leaf springs. Westinghouse trucks have a GSC logo above the leaf spring set, sometimes offset to the right or left.
Some Canadian Alcos used a lightweight version of this truck, with a wheelbase of only 8 feet 10 inches; It lacked the leaf springs found in the other versions.
Most renditions are of the GE version, I know of none of the Westinghouse version. Among PRR models equipped with AAR B trucks were the Baldwin DR-4-4-1500 and RF-16 sharks, RS-12 and DRS-4-4-1000 (with the Westinghouse version), the Fairbanks-Morse H-20-44 (also Westinghouse), the GE U25B, and the Alco DL-640(RS-27), RS-1, RS-3, RS-11, FA-1, FB-1, FA-2 and FB-2, all with the GE traction motor version. The version under the Roco FA-2 and Shark is not correct for either, but does have 4 leaf springs as is correct for a Westinghouse variant. GE versions are available from Proto 2000 (also found under the MDC RS-3), Atlas, Stewart, Walthers, and Athearn; The Athearn version, also found under some Stewart units, is too short. It's actually an EMD 9 foot wheelbase truck.
Here are renditions from: Atlas/Kato RS1("friction" bearings) Atlas/Kato RS11 MDC/Proto 2000 RS3 Model Power/Roco Sharknose B
Fairbanks-Morse C-Liner trucks
Starting with the F-M C-Liner, Fairbanks-Morse designed their own single-equalized B truck, which they also used under some of their H-16-44s, including those of the Pennsy. The Pennsy C-Liners, not surprisingly, also had them. They were designed to house a Westinghouse traction motor, though later they had F-M-designed traction motors. They had a 9 foot, 4 inch wheelbase. Bachmann's H-16-44 is equipped with these trucks, and Train Station Products makes sideframes to fit Athearn trucks.
GE Electric unit B truck
GE used a different B truck design under the Virginian EL-2Bs of 1948.
Alco Blunt trucks
Before switching to the standard AAR Type A truck, early Alco switchers, the S-1 and S-2, came equipped with a switcher truck designed by a man named Blunt. It had an 8 foot wheelbase. When they switched to the standard truck, the model designator also changed. The truck was phased out in 1950; John Kirkland reported it was due to pressure from the AAR. Atlas makes a model of this truck, and Train Station Products makes a sideframe set to fit the Athearn switcher truck.
Alco Black Maria
Another Blunt design, found under the Black Maria testbed units.
Alco Hi-Adhesion truck
Baldwin Batz truck
This truck had a wheelbase of 8 feet, 4 inches, and used 40 inch wheels.
It was a Santa Fe design used under license by Baldwin, and could be found
under some of their early switchers.
EMD HT-B truck
Used on GP40X.
Rockwell/LFM FB-2 truck
Adirondack FB-2 truck
EMD Flexicoil B truck