Croudson joined the Pilgrims last summer after his release from Town. The 'keeper failed to displace Boston No 1 Paul Bastock.
Chapman made the journey into South Lincolnshire in the summer of 2002 after his shock release from Town.
The passionate leftback was a regular during his two years at York Street and was even club captain under former boss Neil Thompson.
Like their fellow former Mariners Peter Handyside and Tony Gallimore, both will no doubt be linked with moves back to Blundell Park.