Okay, here's the C4 to C5 comparison.
The tops of the valve bodies appear to be the same. The the outside of pumps look the same but have different part numbers (the C5 pumps are supposed to have modifications that most builders perform on C4 pumps). C5 on the right.
The bottoms of the valve bodies are different. The inner-sides of pumps are the same (same part numbers too). C5 on the right.
Housing are almost identical with the exception of better fluid channels in the C5 (on left) and the fine thread band adjusters. I guess I forgot to pull the sprag and shifter linkage when I put the C5 in storage.
The C4 valve bodies fit the C5 case, and vice versa. C4 is the better valve body.
Notice the subtle differences in the valve body passage.
Even the shaft housings are identical.
Drums, gears, etc all look the same.
Hope this is helpful to you or someone else.