"Stock engine"
very few muscle cars have anything but stock engines.
Especially after 74 (ADR27A).
The SLR 5000 (L31) engine was in everything from a stateman to a one tonner.
I like to think my Sandman (L31) has the same engine as the all conquering A9X.
Different exhaust manifold and no fan, but the engines the same.
Chrisp