Paul Cullen has reacted following a disappointing run of form that culminated in a 30-16 defeat against rivals Leigh last week.
Allen, who re-joined the club from Barrow in the close season, replaces hooker Mark Smith, currently sidelined with a fractured cheekbone, as captain.
Webster has left to join Hull FC as assistant coach, while former Castleford man Ford has been told he will not be considered for selection for this weekend’s match against Batley, and has been given permission to speak to other clubs.
Vikings CEO Alex Bonney said: “Paul Cullen made it clear that there would be changes following recent performances which have fallen below his acceptable standards. His ambition for our club is to compete and win at the highest level – he knows what this will take, and he is willing to make some tough calls to get us there.”