QC actions are extremely overrated
barrel vice and if you want a torque wrench. add wrench flats to the barrel and you need neither
besides that why you would ever want to drill and tap an action is wayyyy beyond me
Why just buy another (used?) Mark V rifle and either get a smaller caliber OR strip the barrel off and rebarrel in the caliber of choice.
I've never really understood the benefits of a switch barrel unless the action is some high end work of machining.
I recently had a good Rem 700 action rebarreled to a Shilen Alternut heavy contour barrel and the cost was around $700.