In FAST, they could be big-inch motors, but Pure Stock is supposedly enforced.
L89 is a 427, L78 is the 396/375HP deal. Both run pretty darn hard.
Seems to me the Cuda should've had 4.56s, though I was under the impression that the max factory ratio was mandated.
IIRC, to get 4.88s in a Chevelle, that was a dealer-installed ratio - I could be wrong, though.
I seem to recall that the 1st-gen Z28 could be factory-fitted with 4.88s.
I'm thinking the smoke @ shutdown is due to "loose" engines and the high vacuum is pulling oil on decelleration.