Current flow is what matters. Current flow is always the same through the armature. Direction is determined by current flow through the field winding. F1 to F2 or F2 to F1.
Though I mentioned it, since that is often done for a SOA, I can't tell from the photos that it has been cut and turned. I think you need to clean the areas of the knuckle welds really well and take closer photos. I think you may be looking at the stock welds.
The new and old spring perches...
Yeah, it's an M416 built in 65. Someone must have had a laugh when stamping that model number onto the data plate. I have one. They're not all that rare, but it can be difficult to find them in good condition. They'll go anywhere from $500 to $1500. The value is what somebody wants to pay.
Hard to say from your photos. Are those spring-over spring plates parallel to the original spring-under spring plates? There's an OEM weld between the knuckles and the axle tube. Is it possible that's all you're looking at?
The plugs are tapered a little with the larger diameter on the outside. I drilled and tapped them for the bolts and used the bolts on the inside to pull the plugs in tight from the outside.