Robert,
The new AMC heads, unless AMC has recently made a change, should have new VW
exhaust valves put in. The casting on these heads is better than VW but the
valves are not. They commonly have problems under 40,000 miles. I've pulled
many AMC heads myself with burnt or sheared valves.
http://www.benplace.com/amc.htm

-Mike

tevisengineering.com
(too busy working on vanagons to finish my site, but getting close)