I've run 11 speed Shimano cassette with 11 speed campag, worked fine. The spacing should be the same it's just the freehub that's different.

9 speed will be different enough - you will probably be able to make well enough but you'd probably need to set up the indexing to be best in the gears that you use most regularly somewhere near the middle of the block and let it "take up the slack" at bottom and top.
11speed is interchangeable between Campag/ Shimano/ SRAM - I'm currently using a Potenza cassette with eTap, herself an Ultegra cassette with Chorus EPS, and I've also run Ultegra with eTap.

I inherited a bike with a veloce groupset, and was never quite happy with the rear shifting.

Then I discovered that it had Shimano wheels and cassettes - and that the campagnolo cassettes have a different spacing and freehub splines.

Wanted different ratios, anyway, so ended up buying a cassette that had campag sprocket spacing with Shimano spline pattern - job done.

I don't have that bike, anymore.

Let me dig out the part number...

Ok, the cassette was branded 'Ambrosio' but a quick look shows that it was 10 speed only, so you'll probably have to go with the Miche

https://www.sheldonbrown.com/cribsheet-spacing.html#k7fw

First number below is c/c of cogs, second is thickness of cog, third is spacer width and last is the total width of he cassette

Campagnolo
9-speed 4.55 mm 1.75 mm 2.8 mm 38.2 mm
Shimano
9-speed 4.34 mm 1.78 mm 2.56 mm 36.5 mm
SRAM
9-speed 4.34 mm 1.8 mm 2.54 mm 36.5 mm

The bit that is critical is the 2.8mm spacer

My old Campag gear has a cassette made up of loose cogs and the 2.8mm spacers, but can't seem to see the spacers anywhere online now

Yeah I was adamant they were. I ideally want all the gears to be working perfectly as well so I will have to find a cassette. If anyone has one just let me know.

Cheers for the replies aswell

If you have Mavic helium’s why not swap freehub from Shimano to campag?

Otherwise, what has been said is true, ambrosio is a 10speed only solution, 11 speed is the same spacing

Marchiso ? May work but rare.

https://www.acycles.co.uk/mavic-11-speed-freehub-body-campagnolo-ed11-8mm-9mm-5946.html?gclid=EAIaIQobChMIh-Hx9_SQ4AIV7bztCh0tzwLNEAQYBSABEgIl5fD_BwE

May need spacer for 9 speed

Check first

TimpP has the main information the difference is not that big.

I the 2003-2004 season 8 months like that Campagnolo Chorus 9 speed group ultegra casette on dura ace hubs. Used to replace 2 or 3 from the shimano spacers by campag one(recover from your old casette to get the sapcing closer(the difference is only 1.5 mm to start with.

Never had any complaits won me 6 or 7 races and hilly terrain means the whole casette range was well used.

11 speed spacing of campag and Shimano is identical in the real world which is nice as campag cassettes are a fortune.

10 speed campag shifters work with Shimano 8spd mechs and cassettes but that’s a bit niche.

No other combinations work.

I've respaced a Shimano cassette with Campagnolo spacers to make it work - sadly, with the passing of Chris Bell at Highpath Engineering, the easiest solution might be a free hub swap. Unlike Shimano, Campagnolo cassette spacer vary across the cassette. OP I probably have a set of Campagnolo 9-speed cassette spacers I can send you for the price of postage.

I run a shimano 9s cassette with campag 9s.

Works well enough for me.

This might help you.

http://www.jtekengineering.com/shiftmate/shiftmate-compatibility-charts-choices/

Buy a JTek shiftmate

Im going to try the shimano cassette first then use the spacers form the Campagnolo cassette I have if that doesn't work.

Cheers