Early LA motor compared to Later LA motor?

lower compression is correct after 1970 starting in 1971 same valves on a 2bbl 318 LA motor,,,but on a cop car 318 they used the 360 head,,which would make even less compression from every thing ive read,,,

find a chiltons or a motors manual,, and compare the years,,or go to

www.allpar.com search 318,,