Campy 9 speed wheelsets

Hello!
I have a few questions that hopefully the Campy Experts on these
groups can help me out on:

My winter training bike is a mid-90s CroMoly frame Bianchi I upgraded
with Campy triple Racing T and newer Veloce 9 speed shifters. The
cassette/rear hub is the original 8 speed and works OK with the 9
speed shifters, I just have that extra "click". My other bike
(Kestrel Talon) also has Campy triple Racing T and Centaur 9 speed
shifters and I hope to eventually get a pair of Zipp 404 carbon wheels
to race with on this bike.

Ultimately, I would like to have 9-speed cassettes on both wheelsets
so that I could swap wheelsets between bikes. That's where my
question comes in as far as advice on how to do this. The 8 speed
gears on my current wheel has 8 notches to slide the gear onto the
splines on the hub (I think it is called the EXA-Drive system). From
pictures I have seen, it looks like newer 9 speed cassettes have a
different spline pattern than the 8 speed. I can't tell from the
photos whether these 9 speed cassettes would work on my 8 speed hub.
Do I need to replace the 8 speed hub to work with all 9 speed
cassettes? Are there different spline patterns between the different
Campy 9 speed cassettes (e.g., Veloce and Chorus)? Zipp's website
says that the 404 wheels are compatabile with all Campy 9 and 10 speed
systems, so I definitely want to make sure I get the right cassette(s)
to use on these wheels. The cassette I am seriously considering for
its low range gearing is the Veloce 9 speed 13x28.

Thanks in advance for your help and advice!
Andrew Hall
Lancaster, OH