combustion chambers are different use a 2wd head on a 4x4 block and pistons lowers the comp ratio and ups it when a 4x4 head is put on a 2wd block and pistons.

more torque is also gained on a 4x4 head.

early 3dr and saff heads suffered from gasket failure due to the water galleries being bigger in design (exhaust side)

prices varya lot due to head thickness (how many times its been skimmed) virgin heads are about 139 mm ish and ford state min thinkness of 138.68

On a 4x4 head the oil is fed from the head to the turbo.and also has a different design of front cam bearings

Hope this helps