I have previously cut the back mounting point of that bracket off, and used just the front header bolt, instead of using both header bolts on either side of the #1 header pipe. Spacers will work, but I have also had good luck with using a stock manifold bolt, and spinning a nut all the way onto the threads of the end that screws into the head, and using that to hold tight against the header, and using the other end of the bolt with the stud protruding from it to hold the AC bracket.
Martin