I was going to post this under the Rivarossi repowering thread but it wouldn't add to the discussion as the components I used are no longer available.
In the early 1970's the AHM-Rivarossi C- Liner was the most affordable 2 rail O scale diesel on the marker, predating the Atlas F9 by several years. With a young family and funds tight, it was one of my first O scale locomotives - and a big disappointment. After several laps around my oval "starter" layout it became apparent that the Rivarossi drive just couldn't pull a decent length O scale freight train. For several years the unit sat in a box while I worked on other models (and moved to a house with a larger basement). Later in the 1970's Central Locomotive Works and All Nation announced repowering kits to replaced the anemic Rivarossi drive. A May 1980 O Scale Railroading article by Bill Losee on kit-bashing a FM C-liner B unit inspired me to look again at the AHM-Rivarossi diesel. I decided to build a prototypically detailed set of Pennsy A-B-A C-liners using repowered Rivarossi bodies. I picked up three less than mint units at a train show and ordered 2 All nation repowering kits. The kit bashed B unit would be a dummy. I chose the All Nation drive as they reused the correctly detailed (wheelbase, drop equalizer) Rivarossi FM side frames, while Central Locomotive Works' used AAR type B trucks from their ALco FA1 kit. Both AN and CLW's kits had 40" diameter wheels, while prototype FM C-Liners rode on 42" wheels. The AN kit repowering kit used several of their EMD drive components including a centrally mounted double shaft open frame motor and Delrin chain towers on each truck. Brass bushing inserts were fitted to the plastic side frames and mounted to U shaped bolsters. This approach enabled the trucks to equalize. For several years I was pleased with the look and performance of the C-Liners. However after a decade of running the sintered steel wheels treads began to pit badly, accelerating build up of black "gunk" on the wheel treads - further contributing to electrical pickup issues and pitting. It got to the point that before monthly operating sessions I had to clean the wheels.
Disappointed with their performance in the mid 1990's I did a second repowering when a small quantity of sprung FM trucks were offered Car Works. For this repowering project I fabricated a heavy sheet brass frame while saving the fuel tanks. For the drive train I used Pittman can motors, NWSL flywheels, Car Works trucks, and Overland gear boxes. With matching axel diameters it was easy to press 42" CW wheels on geared OM axels. The upgrades improved both performance and appearance.
In 2008 (new house, new DCC layout) the units were upgraded a third time with DCC sound decoders. Some 45 years old they are running better than new pulling 30 car freights up and around Horseshoe Curve.