There was some dicussion a while back on the different cylinder heads for the K241-K301-K321 motors. Here is what each different head looks like.
High compression/LP head:
An easy way to tell if you have if you have this style head is heart shape area in the valve area and a flat spot below the spark plug. This head was found early K241 motors.
Low compression head:
This head like the high compression/LP head has the spark plug in same area. The area above the valves does not have the heart shape like the High compression/LP head does. There is a valley/low spot below the spark plug.
Spark plug above the exhaust style head:
Biggest advantage to this style head is having a better fuel burn compared to the other style heads. The valve pockets are bigger so there is clearance for bigger exhaust valve in some of the K301-K321 motors. The head in this picture will be going on a puller motor (stock class).