Pretty much gonna echo what has been said about the Revell F-bodies. You can mix and match the rest of the goodies from the Revell C5 Vettes, C6 Vettes, Silverados and SSRs to get just about any LSx motor in scale. The F-bodies will get you the T-56 stick shift; the Silverado and SSR the automatic.
Here's my Revell LSx crate motor for my '69 Nova:
'02 Camaro block and tranny.
C5 Vette accesories, intake, heads and beauty covers
Silverado oil pan