I will temper my opinion by saying I've personally never run a set of the CV's but...
Stay away from the CV's!!
The early 650 CV's are not the best designed carburetor, and few performance parts are available for them. Not the easiest to work on either, based on what I have seen on this forum. And if I remember, they're only 26mm, which is larger than the 550 carbs, but the same as the earlier 650 carbs.
I would go with the earlier '79/80 head, and then run CB750 carbs as the earlier heads have the same spacing as the 750's. This gives you 28 mm carbs and plenty of available parts for tuning...