The intake manifold end/alignment posts on both ends of the the head were used on Chevrolet Stovebolt Sixes; however, bolts were used at both ends of the same era GMC sixes.

I think that people have reported that they have removed the Chevrolet end studs and replaced them with threaded boots. I do not remember if the Chevrolet end/alignment studs were originally press-fit or threaded?