If you have the holes in the head for the injector ports, its either a B20E head or the later (1972) B20F head. This link gives you a quick guide to identifying a B20E versus early or late B20F head.

http://www.v-performance.com/articles/volvo_b20_head_identification.html

On my 1971 142E with B20E, the alternator adjusting bracket does not mount to top of the head. In the last photo on this web page you can see the alternator bracket attaches to a hole just above the head gasket mating surface.

http://www.vclassics.com/motorsport/engines.html

You can also just barely spot the hole on the front face near the top of the head by the rad hose outlet. My B20E has a similar hole. It has never been populated so I don't know whether it is threaded or not. Would not be that hard to cut threads if it isn't threaded.