The AMC heads are aftermarket replacement heads for the Type IV engine. They can be ported, and will accept larger valves, but I believe the combustion chamber shape isn't conducive to high compression without some serious mods.
There's a fellow who has taken 2.0 AMC heads and made them better than any Type IV head based on a stock casting. Relocated plugs, large square exhaust ports, and 44 x 36 valves.
http://www.shoptalkforums.com/viewtopic.php?t=76337