I have a dilemma in that in my desire to complete my A/C installation, the location of the pulley mounting hole on the upper right front of the head is missing the normal threaded hole. There is only one other threaded hole in the vicinity and that is occupied by the alternator bracket. In viewing photos of other 1970 A/C equipped 1800's, just to the right of the water jacket plug/disc is where the pulley bolt is mounted. Was I misinformed by the seller that my mounted cylinder head is the original that came from the factory or is it a replacement B20 from another model? If it is a replacement and not a "E" model head, my compression ratio would not be as designed and completion of the A/C system is not possible. Were their two different heads installed on B20E's?