For the 216, there really isn't much gain to be had in the cylinder head department, though installing larger valves and porting can't hurt. Their ports are much smaller than in the 235 and 261 heads as are the valves. The later 235 and 261 heads can benefit greatly from using the available 21st century cylinder head machining and porting technology currently available. Also, the GMC rod swap is still an additional way to further improve the rod length to stroke ratio, plus add a better rod. A performance book explaining this procedure along with other Stovebolt performance books are fixing to become available.
