I just purchased a Concorde Mistral with Columbus Gara tubing and would like to transfer my Campagnolo group from an SLX frame that is too big. The Concorde frame has a front derailleur mounting bracket on the seat tube just like the SLX frame I already have. I understand I would be losing the indexed feature the Shimano has, but would it be possible?
As Pete H has commented, a partial swap will probably not work out.
On frames / bikes of this age, things were easier as compatibility was not quite so much of an issue, so some elements could probably work together OK - but if you are not sure / inexperienced, best is to swap everything.
Worth checking, though, that the threads for the bottom bracket on both frames are the same - some Concordes used to be Italian threads, your existing frame may be Enlish and they are not interchangeable.
To check which you have, measure the width of the shell, width-ways (i.e don't try and measure the diameter) excluding the cups that screw into it - 70 mm Italian, 68 mm English.
With some customization the partial change is possible.
Get a rear sprocket cassette which mounts on Shimano freewheel but is designed for Campagnolo - they are available. So, you can use your old wheels.
Crankset, chain, derailleurs must be changed completely, cross-compatibility with Shimano (with chains in particular) there happens but is neither flawless neither recommended. Be careful with cranksets - your Campagnolo crankset may be incompatible with bottom bracket in the frame, therefore it would need to be replaced.
Levers - it is technically possible to use Shimano ones, but don't. Just for one simple reason - Campagnolo levers are more comfortable and replacing levers is not such a difficult task technically.
Brakes - these will work whatever they are, Shimano or Campa.