I was interested that the leading dimensions of the 4-8-2s and 4-8-4s were so similar, particularly regarding cylinders and driving wheel size.
The 4-8-4 had a boiler barrel similar to that of the 4-8-2, but fairly obviously a longer grate (by about one foot) resulting in a longer locomotive.
One thing I didn’t expect was that the earlier 4-8-2s all had Type A superheaters whiile all 4-8-4s had Type E superheaters. This included 4-8-2s built after the initial batch of 4-8-4s.
The final 4-8-2s (6060 onward) had Type E superheaters. I don’t know about the preceding U-1e class, I haven’t seen a diagram, but the similar U-1ds definitely retained the Type A superheater.
The final locomotives, both Mountain and Northern, U-1f and U-2h both reverted to outside frame leading trucks, and were very similar in overall appearance.
It is clear that CN saw a continuing role for both types in the steam era.
Peter