[Dave Z]

FWIW there's a bunch of info at -> RB Engines: Chrysler’s biggest V8s
Two things to remember about horsepower ratings.
1) As someone noted earlier, they were, um, imaginative at times.
2) BHP vs HP - gross vs net power.

 

[Dave Z]

GASP! You...you...you mean sales people sometimes "tweak" the facts??? Who'd a thunk it?

In this case, marketing people, but... before the 1980s, a lot of power figures were largely imaginary, and especially before 1971, in both directions.

 

[Dave Z]

Some think once the engine's been broken in, zinc and lead aren't required often. Going back to when I looked into it, a while ago. Occasional additive can't hurt, especially zinc.