Clarke last played in the 1-1 home draw with Dagenham on December 5 while Boshell's final game came in the shock FA Cup loss to Bath at Blundell Park on November 7.
Heywood, who signed a two-year deal in the summer of 2008 after joining from Brentford, has made just one appearance this term - in the 4-0 defeat at Port Vale in September.
Source: Team Talk
Source: Team Talk