although it is possible to install several aks-74u parts on an ak-74 and one can modify others to fit (such as the action cover) to fit, most are specific to the krinkov.
rear trunnions are interchangeable, as are carriers and fire control parts.
front trunnions on the krink are identical with the exception of the stock latch pivot hole.
the gas tube and rear block/action cover pivot (what would be the ak-74 rear sight block is krink specific...although it can be fitted to an ak-74.
the short gas tube is krink specific, but again have been fitted to ak-74's by modifying the bbl.