Generally, triples use a longer BB spindle, so you probably need to replace the BB as well to maintain chain line. I'm actually doing something like this with an old Cannondale, converting from a triple to a double. The triple uses a 122.5mm spindle, whereas the double uses 107. That's a pretty big difference!
Shifter should be fine since Campy doesn't try to index the front. But you'll have to adjust the limit screws in any case or the chain will fall off whenever you downshift. Or upshift, probably.
Regarding chain length, it might work or might not (i suspect not). One way to check is wrapping the chain around the large chain ring and largest cog and then add an inch. You really shouldn't ever be in that gear, but that sizes it correctly.
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