be careful some 305s have one bolt for the manifold off the alignment for the exaust usually onr at the end of the head and you will have to drill and tap a hole in in the proper place usually some heads have two holes on the flange in this place and some dont my 305 heads from 84 camero with crossfire injection had two holes and my 81 casting 305 heads did not i dont know why they did but they do have fun im still having to work on body work so im not in the fun part yet