You mean make new front panels so that the port is an opening all the way across the front instead of just the two port cut-outs ?
Yes
Then a whole new top port ducting for the top speaker and replace the baffle that's cut up? Do I have you right?
Yes
Should the Front panel (that the speakers bolt to) be two pieces separated by the port opening?
Yes
I think you mean to make it this? http://sunn.ampage.org/site/schematics/foldinghornr.gif
Sort of. That appears to be a 2000S cabinet in the diagram you linked to, same basic layout.
If I were you, I would drop those D140's into the cabinet as it sits, any see how it sounds. You may end up getting me to modify a 200S cab with a jig saw instead of you fabricating pieces for your cab.
I think the port measures 4", but I'm not sure. If the baffle you have will allow the 4" port, you should be able to just use it instead of buying a new sheet of wood. It looks like the ducting is all there on the bottom of your cabinet, albeit carved on. I would think you could emulate the boards and just invert them to create the top ducting, and then replace the chopped up bottom duct board.
Let me know if you are going to do it, and I'll measure a 200S port for you to make sure about the 4" thing.
