It sounds very much like the cylinder head is somehow insulated from the rest of the engine. Possibly a layer of rust has built up between the head bolts and the head itself, which is unlikely but it's all I can think of. Pull one of the head bolts out and examine it and its washer and the area around the bolt hole in the head. I suppose that the head gasket is providing its share of insulation as well.
I, on the other hand, am replacing crankshaft seals in my '84 Trac Clipper, which is a Korean Batavus. It's not as difficult as advertised, for they come out from the outside.