The one I sold which I am pretty sure was open was on a 655" deal we had tat i bought used. We freshened it up and made some big changes to since it is going in a bracket car we went with a single 4. I was pretty sure it was open but so many engines of our own around here and getting older aint helping. I thought/ assumed the tent version was the older one. The 655 we bought was not that old but who knows..I know I sold it to my buddy in Canada to replace hos tent version which he as had for long time, at least a 15 years I have known him. He crashed his car and intake got hurt when it was sliding on its roof and the old BG Demons got destroyed(thats how old this was). Sold him the tunnel ram and a pair of Book carbs I had for it so he could fix his 655.