Never heard that one about Chevy looking at Packard V8s. They sure could've done worse. Actually did, from what I've heard about the inefficiency of their early design BB. But what amazes me is that they essentially borrowed a very cumbersome, heavy truck engine (about 664 lbs "dry for the 348) to fill the gap, and somehow sold it on the basis of being a "Chevy." In any car, it made for a plowing, overweight front end. (As you can probably tell, not my favorite engine--except for the sheer audacity of it).
But, what about your previous question? I couldn't find much more than my original guess, except that the "W" or Mk I was available in 427 cu in for the Impala Super Sport. This was a 427 "W" not to be confused with the later 427 "W".
Generation 1 Chevy BB
From 1958 to 61, 348 (used in trucks until 1964)
1963, 427 "Z11" for racing. 57 produced (stroked 409 dual carbs 13.5:1.
Didn't find much on the Mk I
except the 1958 "Scarab" Mk I which used a Corvette 283 bored and stroked to 339 and raced against European sports cars.
Here's what I found on the MkI and MkII:
Inside Chevrolet Engineering, it [the new non-W race motor] was called the Mark II, a 427ci V-8 that had no bloodline with the 409, which was dubbed the "Mark I."
From this site: http://www.superchevy.com/features/su ... k_chevy_engine/index.html
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