Kenny,
Not sure of the pipe measurements, but the way to tell which style pipes you have is...early style the last 1in. or so of the pipe is slightly larger dia. than the rest of the pipe & has 2 slots cut in the end of it. The late style has a flare on the end of the pipe where it fits into the head. Which style exhaust are you trying to install? Yes, the spigots will work if you remove the studs.
If somebody put in the studs to accept a late model exhaust they should come out fairly easy. HOWEVER, if this is a late model head with the factory studs they are extremely hard to get out. Not uncommon to break one or two doing this. Then you have to remove the head & take it to a machine shop...gonna be cheaper to get a correct second hand exhaust system.
But I have all the hardware for either style...