One 1970 Chevelle had 2 keys,(primary,secondary),that opened all it's respective locks.
Model design or engine equipped had nothing to do with it.
All 1970 Chevrolet vehicles,be they made early or late,came with the same letter profile code.
"J" on the primary & "K" on the secondary,but not exact specific number code,obviously.
Letter profile codes were alternated every 4 years..1970,1974,1978,1982.
Rich Fields did an excellent in depth write up on this..
http://www.camaros.org/keysandlocks.shtml#intro