I have a 760 with two barrels (complete factory assemblies) both in 308, one barrel is a factory carbine, the other is a standard rifle barrel. Here is a quick summary of my research:
760 barrel assemblies will interchange with other 760's but not 7600's. 7600's barrel assemblies will interchange with other 7600's but not 760's. The the actual interchange is not difficult and somewhat similar to an 870 shotgun interchange.
It is difficult to find a barrel assembly in either model- the barrels usually go for near the price of a complete gun. If your pump calibre is in a short cartridge, 243, 308 etc you will need a spare magazine if you want to rebarrel to a long cartridge 270, 30/06, 35 Whelen. Short cartridges in short magazines, long calibres in long magazines. Action lengths and bolt faces are the same for short and long.
Obviously a 223 model is a wild card; the bolt face will not fit other calibres.
I hope this helps. I would be interested in knowing if anyone has rechambered a 760/7600 to a magnum calibre.