somehow, I think we are speaking past each other?
The splashwell wasn't a difference in the two models, it was an update that occured to both in 1960.
The hp rating wasn't a difference, it was consistent to both. (and most likely increased due to the splashwell holding things together better)
The only main difference in the two models, the Malibu and The Coronado is the presence/absence of the rear seat backs.
Or perhaps on older hulls needing restoration, the evidence of where seat back brackets used to be. (the holes where the rivets were)
All other features of construction were basically the same.
When the models were updated through the years, both models received all other updates together.
When the splashwell was introduced, both hulls received the splashwell.
The Malibu was targeted to a family for joy riding and could seat more people comfortably with the complete rear seats.
The Coronado was targeting fishing trips, too, so left the rear seat as a bench only to accommodate moving around the boat with a fishing pole.
If you see the triangular brackets -or the holes where they were- attached on the inside gunnel above the rear seat frame, it's a Malibu.
The light blue boat pictured above is a Malibu. It has rear seat backs and the factory braces against which they are mounted.
The following factory graphic from 1960 shows these brackets and a splashwell on a Malibu.
