Check out rimfire central, there are a few guys there who have converted their .22LR 597's into .22WMR 597's. As far as I (and they) know, the receivers are identical between the LR and WMR rifles. It makes perfect sense when you think of production and warehousing costs associated with making different receivers for the same model rifle.
From what I recall, all you need is the bolt, barrel, return springs, and the lower plastic receiver with the longer mag-well.