84 - 92 Corvettes

I work at a machine shop and would like to know what is attached to the 3/8-16 taped hole (boss) on a 84-92 water pump. I am looking into fitting a sm block chevy pump for the 84-92 application. Is there any clearance issues or does it just bolt down a bracket. The pump I am going to use has a larger boss than the original equipment pump?