Yes the smaller four. The top, should just pull right up if broke. The bottom is where I was saying "punch" them out.

The housing is not threaded. There is a nut in the bottom of the lower part, then the bolts thread into those nuts to "clamp" it closed.

 

Ok, wait, I must have read this wrong. If the head of those four bolts just spins and won't come out, the nut at the bottom has come out of the housing and is "rusted" to the bolt and the "wings" have rusted and allowing it to spin. Drill the head off, or "something" then the top will come off, then see if the bottom part just slides out...kind of tight so you might have to pull the lower part all the way out.