After fitting the motor, gearbox and wheels I tried it for size with the completed running plate assembly and after a small amount of filing it all fits perfectly. My standard choice is for a Mashima 9/16 and Branchlines RSL gearbox. The coupling rods are secured at this trial stage by plastic sheathing from layout wire. They will eventually be soldered on with Romford crankpin washers at a later stage.
Here the cab assembly, bunker and tank castings are put together loose just for a trial fit.