C&O H4 vs H5

[Vidshooter]

I have an H5, which is a great loco.

I understand the prototype H5 was a USRA, whilst the H4 was C&O design.

Can anyone tell me the difference in the models between the H4 & H5?
Are there any significant prototype differences not represented in the  models?

Thanks

[ryeguyisme]

right off the bat, the front cylinders and the cab, I'd have to give them a more thorough look to see it all but thats a first off of memory