Or Not

“If only the main driver was swapped end for end, whichever side is last to have the rods put up will find the main crank 180 degrees out.....”
Actually not, Matt. Right hand lead is right hand lead regardless of which way the wheelset is turned. Picture a wheelset sitting loose on the shop floor, the crankpins will be 45 degrees off top quarter. As you stand facing one wheel, the crankpin will be 45 degrees to the right with right hand lead. If you walk around the wheel set and face the other wheel, its crankpin will also be 45 degrees to the right. If you stand in that spot, lift the wheel set with a crane and spin it around, the other wheel as it comes around to face you will still be 45degrees to the right. Identical.
The eccentric cranks are another matter. If you look at the left side of a K-36 with the crankpin at the bottom quarter, the eccentric crank leans to the left, toward the cylinders. If you walk around to the right side of the engine, and move the engine so that crankpin is at the bottom quarter, the eccentric crank leans to the right, also toward the cylinders. Mirror image.
I have swapped a wheelset end for end during an overhaul because doing so caused that wheelset to be a better fit with the rest of the machinery, but it wasn’t the main axle for exactly the reason we are discussing in this thread.