I have some of each, the 3-brg heads from 67 and 69 Kadets, 4-brg heads came on my 70 GT and 74? Manta parts donor.
What does Stage 2 mean?
It's a good price so far, too bad there are no lifters with it.
Also, keep in mind a 4-brg cam will work in a 3-brg head, not the other way around, there are posts about this...