hmm, I’m a little confused by what you mean when you talk about bolting to the back of the alternator…there only should be mounting points on the front (pulley) side of the alternator. However, if this isn’t a stock setup, maybe someone jury rigged some oddball mount?
Maybe the info and pics in this link would help? http://www.jeepforum.com/forum/f8/alternator-mounting-bracket-889658/