I actually thought about that yesterday when I was doing an oil change. I imagine it has to come off and be dismantled. It does not look overly complicated. I will have to dig into the shop manual. One of my concerns is that oil supply line and the little o ring at the bottom. Does the o ring come out with the tube? Some information sources I have researched in the past seemed concerned about messing with this as it is no longer available at least according to them. I have left it alone till now but eventually something has to be done. I don’t think I have had someone with your level of experience with the 223 to give guidance. The oiling at the top end has been something on my mind....just not sure how much is supposed to be up there.The aftermarket intakes usally will have the boss cast on the intake just like on a stock 223 intake so that your throttle and kick down linkage should bolt right on. On your rocker wear did you make sure the rocker arm shaft is clean inside so that its oiling properly on all the rockers? Best of luck.
I noticed in your other intake photos that they also had the boss for the linkage. On the stock manifold the linkage is positioned where the rear carb would be on a dual intake. The linkage position on the dual intake would put it in the middle with some type of extension or other modification to get around the rear carb on the inside and link up with the kickdown rod. I noticed on the Offy website they mention that with their dual intake there is not enough clearance with the hood in passenger cars. How about the other vintage intakes. Is there one that has clearance?Here is a pic of a Fenton manifold. It has the same holes for the linkage as your stock manifold.
I did run it with the valve cover off with the oil return line popped off and after a few minutes I got oil coming out of the return hole. I will do a more careful check of each rocker in the next day or so. I also have no concerns about taking the whole assembly apart for cleaning. I just have to make sure I can source a few of the parts I would need like the plugs for the ends of the rocker tube and that pesky o ring on the oil supply tube.It dosnt need to have very much oil to the top end but it can't be dry, try running the engine at idle with the valve cover off and see if all the rockers are oiling.
I had a realy nice Clifford Ram Flow single 4V intake with a Holley, in my OPIN its one of the very best 223 intakes ever made and I think it was the only single 4V made. If you could find one of those it could work good on your 1963 and I think it would also be a lower in over all height.
I stood a tape measure on end on the intake with several inches extended and closed the hood. In the position of where the forward carb would be I have seven inches. More in the rear of course. I have the autolight 1100 carb and the overall height from the manifold to the top of the stud is seven inches. The stock breather doesn’t add any height.This is the height with a Holley 1904. Not sure how much there is in a car but probably add at least 3-4" for a breather.