Serpentine conversion question

[EODtech]

I recently pulled off a serpentine system of a 1989 camaro to put on my 68. I ordered the smog delete pulley, it's the same smooth one that come with the gm kit. The problem I ran into is that the mounting hole is threaded and the bolt I have has a shoulder and goes all the way through and bolts to the head. The shoulder won't fit through the pulley bracket. I tried just using two bolts but it needs to be to long to fit into the bracket. I was thinking about drilling out the threads and just not having fore and aft resistance. Hopefully my pictures help. Its the long bolt in the middle of my pictures and the top bolt of the of the idler pulley in the assembled system.

Thanks,
Joe