While I've posted a thread on converting the MTH equivalent to 2R already, I followed the same basic process. See that process here
Converting an MTH 50' High Cube to 2R | O Gauge Railroading On Line Forum
I did decide to use the Kadee #819 extended gearboxes to achieve a closer to prototype look and operation. Using the provided mounting holes I first drilled and taped the holes for 2-56 screws. Once I had the first coupler installed, I looked and prototype photos and decide those extended gearboxes really stuck too far out, while just the standard #818 gearbox didn't extend enough to resemble the prototype. What should I do?
I decided there was enough room to slide the extended gearbox back so that is was closer to the bolster. Once I did that I marked and drilled new mounting holes. place a smal shim at the rear of the extended gearbox and then I reattached the extended gearbox. Slipped the body back over the chassis and was much happier with the appearance and operation. So I did the B end of the car and reinstalled all the screws. See photos below, just having the cut lever to install and some light weathering.
Original Installation of the #819 extended gearbox
TOP View
Finished conversion with #819 extended gearbox slide back toward the bolster
