Mopar Small Block Head info:

1971 was the first year for 360s. They used J heads in cars and trucks. I assume J heads were revised for emissions. The performance X heads were gone and J heads were used for some 70 and 71 340's, with 2.02 intake valves. 71 up 360s, and 72 340's all use 1.88 intake valves. HP heads, 340s and 360s use 4 groove keeper intake valves with .0005 smaller stems. Standard 360 heads used 2 groove keepers and trucks used rotating retainers which move the keeper grooves down on the stem. Stay away from castings with excessive core shift. They are more prone to cracking and thicknesses less uniform. The more time went on the more the castings were compromised for emissions reasons and performance took a back seat, until the 302 and 308 heads which got some of the advanced design from W2 heads. But these are very prone to cracking between the seats.