The EWS Class 66 is a Graham Farish model and was one of the first I purchased that included provision for DCC decoder installation. There is a circuit board along the top of the chassis; remove two clips, solder the decoder wires, rearrange the wires to the end lights (so as to make room for the decoder) and hey presto - a DCC equipped loco. A Digitrax DZ123 fits and works fine.
The locomotive lights are operated using the F0 function. The large fan vent indicates the front of the locomotive.
I've added Micro-Trains couplings to the bogies. A #1130 kit (long shank) fits well, and slightly increases the coupled length to the rolling stock. A shorter coupler would probably foul the buffers, but now I'm mounting them lower it could be reconsidered. See how the top of the coupler insert has been shortened so as not to foul the buffer beam:
I had problems at first with fouling that resulted in the bogie's drive from its work gear not meshing. The coupling was fouling the buffer beam, and pushing the bogie downwards at the end of the body. With the coupling mounted to the bottom of the pocket it is less of a problem now.