If your wife's rifle shoots great as is, I would leave that bolt married to that rifle. Besides, the .223 bolt face and magazine would not accommodate the 7.62x39 based Grendel cartridge, and you can't go swapping bolts without ensuring headspacing is correct. You'd probably be better off looking for another CZ or alternative action in 7.62x39. In addition to CZ, both Zastava (Serbian) and Saiga(Russian) make bolt action rifles for the cartridge, and Browning, Remington, Ruger & Winchester have all offered them in the past. Re-barreling any of the American offerings may be an easier proposition.
Honestly, though, it would be a shame to see a good CZ barrel go to waste, so I would save it for a project involving a gun that was already somehow damaged or neglected if you're set on doing so (it would save you money, too).
